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How To Know

THE FRESH-WATER ALGAE

5^

An illustrated key for identifying the more com-
mon Fresh-water Algae to genus, with hundreds of
species named and pictured and with numerous aids
for their study.

by

G. W. PRESCOTT, Ph.D.

Professor of Botany
Michigan State University

Wgods Hole Oceanographic Institution
Clark Reading Room

MARINE
BIOLOGICAL
LABORATORY

LIBRARY

WOODS HOLE, MASS
W. H. 0. I.

WM. G BROWN COMPANY

Publishers

DUBUQUE, IOWA

Copyright 1954

by
H. E. Jaques

Library of Congress Catalog Card Number: 55-3214
THE PICTURED-KEY NATURE SERIES

"How to Know the Insects," Jaques, 1947
"Living Things — How to Know Them," Jaques, 1946

"How to Know the Trees," Jaques, 1946

"Plant Families — How to Know Them," Jaques, 1948

"How to Know the Economic Plants," Jaques, 1948, 1958

"How to Know the Spring Flowers," Cuthbert, 1943, 1949

'How to Know the Mosses and Liverworts," Conard, 1944, 1956

"How to Know the Land Birds," Jaques, 1947

"How to Know the Fall Flowers," Cuthbert, 1948

"How to Know the Immature Insects," Chu, 1949

"How to Know the Protozoa," Jahn, 1949

"How to Know the Mammals," Booth, 1949

"How to Know the Beetles," Jaques, 1951

"How to Know the Spiders," Kaston, 1952

"How to Know the Grasses," Pohl, 1953

"How to Know the Fresh-Water Algae," Prescott, 1954

"How to Know the Western Trees," Baerg, 1955

"How to Know the Seaweeds," Dawson, 1956

"How to Know the Freshwater Fishes," Eddy, 1957

"How to Know the Weeds," Jaques, 1959

"How to Know the Water Birds," Jaques-Ollivier, 1960

"How to Know the Butterflies," Ehrlich, 1961

"How to Know the Eastern Land Snails," Burch, 1962

Other Subjects in Preparation

Printed in U.S.A.

INTRODUCTION

ARDLY any body of water or moist spot on the face of the
earth is devoid of algae. They are almost as nearly
ubiquitous as are the bacteria which are perhaps the
most widely distributed organisms in the world. The
variety of form and color exhibited by the algae is seem-
ingly endless and Nature has shown no bounds in designing these
ornate plants, many of which have bizarre shapes and specialized
habits.

Because of the bright colors possessed by many algae and because
their extensive growths which develop in ponds and streams, algae
frequently attract attention. The more conspicuous growths of fresh-
water algae are usually referred to erroneously by the stranger as
"water moss," "moss," "frog-spittle," or are sometimes called "pond
scums." This illustrated key is designed to give the student who is
equipped with a microscope an opportunity to explore the world of
freshwater algae and to give the correct scientific name (at least the
genus name) to the more common forms. The student may find to
his surprise that a clot of "moss" will include half a dozen or more
distinct and recognizable plants, each with its own individual char-
acteristics of form, method of reproduction, and life history. In some
collections taken from acid bogs as many as 200 or more different
species may be found.

It is hoped that this book will be a help in identifying the genera
of freshwater algae and that it will serve toward the elimination of the
indefinite and erroneous names under which they pass. To be sure,
the naming of a plant or an animal is not necessarily an end unto
'itself — but identification and naming must serve as a basis for a study
of structure, life history, ecological distribution and economic im-
portance. Just as when one knows the name of a person and so can
then learn more about him (or her), so the naming of algae can be
, the beginning of further investigation for the pure pleasure of getting
acquainted with the world of aquatic life about us, or for scientific
. pursuits.

Having found the generic names of Ireshwater algae, the student
» may wish to identify the plants according to their specific names. For
this he will want to turn to some of the works listed in the bibliography.
An attempt has been made in illustrating the genera of algae to present
the most common species that one is likely to meet, or to give illustra-
tions of several species of a genus. In many cases, among the one-
celled and colonial genera especially, there is considerable variation
in form among the species contained in a genus. The student will

need to keep this point in mind when matching a plant under con-
sideration with the illustrations in the key. A plant in question may
be a species somewhat or quite unlike the one shown.

The generic names used in the key are those of long-standing and
the ones to be found in floras and handbooks the world over. In a
few instances the names have been reduced to synonymy by special-
ists who have critically examined the old taxonomic literature for long-
forgotten synonymies. The advanced student is urged to look into the
writings of specialists if he wishes to adopt the recent taxonomic
terminologies.

East Lansing, Michigan
August 1, 1954

?

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We first met Doctor Prescott when he was working on the Algae of
Iowa as a graduate student at our State University. We've had some
pleasant correspondence through the years since then and now it is a
pleasure to include the results of his years of study in our Pictured-Key
Nature Series.

<

I

H. E. JAQUES

Editor

CONTENTS

Page
Introduction U1

What Are Algae 1

The Phyla of Algae 5

Synopsis of Algal Phyla 10

How and Where to Collect Fresh-water Algae 12

Books and Papers Dealing with the Classification of

Fresh-water Algae 18

Pictured-Keys to the More Common Fresh-water Algae . . 20

A Check List of the More Common Fresh-water Algae

According to Families, Orders and Phyla 189

Index and Pictured-Glossary 199

CHINESE IDIOGRAPH FOR THE
WORD ALGAE.

WHAT ARE ALGAE

LTHOUGH most freshwater algae are microscopic, many
kinds are greqarious and occur in such numbers as to
form the well-known and conspicuous "pond scums,"
"water blooms," or "water mosses." A few genera are
individually large enough to be seen easily without the

aid of a microscope, e.g., the stone-worts (Characeae), or some of the

freshwater red algae such as Batiachospermum.

If it were possible for freshwater algae to grow as large as some
other plants (mosses and ferns for example) and to live upon land,
they would be considered highly attractive indeed and would be much
cultivated as ornamentals. The symmetry of form and the patterns of
ixtemal decorations which many of them possess are not excelled by
the larger plants in beauty. The varied shapes of both marine and
freshwater algae, coupled with their many colors and hues have made

them the subject of observa-
tion and wonderment for a
long time, especially since
the invention of the micro-
scope. Indeed, the microsco-
pic size of most of the fresh-
water algae make them all
the more intriguing, and
since the early days of the
first microscopical club they
have been used for pleasur-
able observation and specu-
lation. It is not the aesthetic
quality alone of freshwater
algae, of course, which explains the amount of interest shown them.
For small though they are. freshwater algae (like some of their micro-
scopic kin in the oceans) have their own economic importance. Their
relationship to aquatic biology problems of various kinds, their trouble-
some contamination of water supplies, and their use in general physi-
ological research constitute just a few of the manv aspects which
lead to a study of them. Purely scientific problems such as their role
in organic evolution, the biology of their reproduction and life his-
tories, and their ecology are common subjects of investigation. Al-
though much is still to be learned from them, the solution, or at least
clarification, of many problems in general biology and physiology
have been obtained from studies of algae. At this time, for example,
much attention is being given to algae in culture for the study of
highly important and practical problems in photosynthesis and the
products of algal metabolism. Some genera of unicellular algae are

1

HOW TO KNOW THE FRESH- WATER ALGAE

being used for the assay and detection of biologicals (vitamins and
growth-promoting or growth-inhibiting substances) in tissue culture
work. Some of the research on cancer involves studies in the physi-
ology and reproduction of algal cells. I

Whatever the interests in freshwater algae may be, the student a
who has access to a microscope can find many hours of fascination
in a few drops of pond watei.

The term "algae," derived from the Latin name for sea-wrack,
has come to be applied to all relatively simple marine and fresh- <
water vegetation. Actually, of course, many different kinds of organ-
isms are included among the plants which lie outside or below the
realm of mosses (Bryophytes), the ferns (Pteridophytes), and the seed-

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bearing plants (Spermatophytes). Included under "algae" are the
smallest and most simple of chlorophyll-bearing organisms, the entire
plant being but a single cell. Some of these may be less than 1 micron
in diameter. At the other extreme, some of the brown algae (Phaeo-
phyta) include the longest plants, in the world. One of the kelps (Macro-
cystis) of the Pacific Ocean, for example, may reach 700 feet, and even
greater lengths have been claimed.

The student soon learns that "algae" include several divisions
or phyla of the plant kingdom, and that there are incorporated even
some groups of organisms, which, strictly speaking, belong neither
to the plant nor to the animal kingdom (Euglenaceae, Dinoflagellatae,
and many of the yellow green algae such as Synura and Dinobryon).
These are forms which usually are treated as chlorophyll-bearing
protozoa in a reference book dealing with one-celled animals. Sev-
eral of the swimming, protozoan-like forms have definitely plant-like,
non-motile relatives, however, which more than justify their being given
a place among the algae.

The reader who is not familiar with the classification of plants and
animals, and with the terminology used for the different categories
may wish to refer to the following definitions.

2

HOW TO KNOW THE FRESH-WATER ALGAE

SPECIES. A particular kind of plant or animal is called a species.
For example, a certain rose, or a particular alga such as a "pond silk,"
or a particular bird is known as a species and is given an identifying
or specific name. Because there is so much (although slight) variation
between individuals which are in general very much alike, the limita-
tions or precise definition of a species of plant or animal is often difficult
to draw and is subject to different interpretations of specialists.

GENUS. All plants which obviously are roses, but not all the same
kind, are grouped together and constitute what is known as a genus
(plural, genera). Thus all different species of roses are placed in the
genus Rosa, the Latin name for the genus. All species of "pond-silk"
are placed in the genus Spircgyra. The genus name, Spirogyra, and a
species name (a particular kind) together constitute the scientific name.
For example, Spirogyra elongaia is the scientific name of a species which
has long cells; fiosa cinnamonea is the cinnamon rose. This method of
naming each kind of plant and animal with a double name is known as
the binomial system of nomenclature. The double name identifies not
only a particular kind of individual but also indicates to what group
(genus) it belongs.

FAMILY. The genus flosa has much in common with the strawberry
genus (Fragaria), and is much like the prune genus (Prunus). Simi-
larly Spirogyra has much in common with another group of species
which constitute the genus Mougeofia. Therefore, Rosa, Fragaria,
Prunus, and other genera that have characteristics much in common
are grouped to form what is called a family. In this case, the Rosaceae
or Rose family. Spirogyra, Mougeofia, Zygnema and some other algal
genera which have characteristics in common and which seem, there-
fore, to be related are grouped to form the family Zygnemataceae.

ORDER. In turn, families which are distinct from one another but
which, nevertheless, have some few characters in common are grouped
to form what is known as an order. Thus we have the Rosales, the
Zygnematales, etc.

MOST ALGAE ARE AQUATIC

HOW TO KNOW THE FRESH-WATER ALGAE

DIVISION or PHYLUM Several orders may be grouped to form
a major category known as a Division or Phylum of the plant kingdom
(or of the animal kingdom as the case may be). Thus several orders
of the green algae constitute the division (phylum) Chlorophyta. In
many instances it may be convenient to subdivide the phylum into
groups of orders called classes. Hence in the Chlorophyta there are
recognized 2 classes, Chlorophyceae and Charophyceae. In the key
which follows only the genus names are given, with illustrations of
1 or 2 common species. For this reason particular species in which
the student may be interested in identifying will not necessarily look
exactly like the ones illustrated. In so far as possible, the most dis-
tinctive features of the genus are shown in the illustrations.

4

THE PHYLA OF ALGAE

HE organisms which constitute what are commonly known
as freshwater algae are extremely 4ive r<3e m form, color,
habit, and in theii habitats. Actually, there are as many
as eight separate phyla or divisions of the plant king-
dom included under the name "algae," (nine if Cryptophy-
ceae of uncertain position are given the status of a division). Hence
to undertake writing descriptively about freshwater algae, one is con-
fronted with almost as great a task as if he were treating all the phyla
of land plants, fungi, mosses, ferns and the seed plants, plus three
additional groups all in one work. To be sure all the phyla of 'algae'
do not include as many families and genera as do some of the higher
plants, but the green algae alone include some ten or twelve thou-
sand species, distributed among about 375 genera. The task of the
writer in describing freshwater algae is not made easier by their rela-
tively small (mostly microscopic) size. Hence it is necessary to employ
special descriptive terms in order to differentiate these minute organ-
isms, and to classify properly the classes and phyla to which they
belong.

In such a treatment as is presented here, only the most common
and best known genera can be given a place. The reader should
have thi.« in mind when using the key. He should avail himself of
other less abridged or monographic works if satisfactory identification
of a plant in which he is interested does not appear possible by the
use of the following key.

The illustrated key is intended to assist the beginning student
and the non-specialist (equipped with a microscope) in identifying
the genera of freshwater algae which occur in the United States.
Such a key cannot be made as easy to use as are many keys to
larger organisms. But an attempt has been made to overcome some
of the usual difficulties by keying out some genera at several dif-
ferent points, especially those which are so variable that selection
of any one set of differentiating criteria for them is almost impos-
sible. At least, a beginning student or one with little familiarity with
the algae, must exercise patience until he has developed some de-
gree of judgment and has become well-acquainted with the meaning
of terms, and until he has discovered to what degree a plant may
vary from the usual character employed in making an identification.
Many times he will find it profitable, if not necessary, to "back-track"
in using the key and follow down both dichotomies of choice before
arriving at a satisfactory determniation. In making use of the illus-
trations it must be remembered that only one or two species of a
genus are illustrated, and that the plant in which one may be inter-

HOW TO KNOW THE FRESH-WATER ALGAE

ested does not have to look exactly like the forms which are figured.
This is true for many of the genera in the Chlorococcales of the Chlo-
rophyta {Scenedesmus, Oocystis, Tetraedion, etc.) and of the desmids
(Cosmarium, Euastrum, Micrasterias, e. g.) also in the Chlorophyta.

For a study of most freshwater algae a compound microscope is
needed which has a 10X ocular, and a 10X and 40X objective. For the
study of the larger forms such as the stoneworts (Characeae) a binocu-
lar dissecting microscope is highly desirable. Best illumination for the
microscope is obtained from daylight because colors of the algal pig-
ments appear more naturally. In lieu of good daylight (light from a
northern window preferred), artificial light from a microscope lamp
fitted with a daylight blue bulb is used, or a lamp which has a blue
filter. Naturally, all optical parts of the microscope should be kept
free of dust, moisture, and finger prints, using rice lens paper for
cleaning. It is difficult enough to see algae clearly when optical con-
ditions are perfect. An eye-piece micrometer is desirable.

In preparing mounts for the study of algae under the microscope,
small amounts of material should be used, and spread out evenly in
a thin layer. Dense clumps and opaque masses of algae in a micro-
scope mount produce only disappointment and headaches.

One of the primary difficulties with which the inexperienced stu-
dent is confronted when first using a general key to the algae is that
of detecting and identifying colors, green, "blue-green," "yellow-green,"
etc., to which the key makes reference. Pigmentation in the differ-
ent algal groups is a fundamental characteristic and one which is
very helpful in making identification. But yellow-green algae may at
times appear decidedly grass-green, and the brown-pigmented algae
may have a distinct tinge of green, especially when artificial light is
used for the microscope. Hence, other characters or a combination of
characteristics excluding or in addition to color must be employed to
make a choice in the key. Suggestions are given in appropriate places
in the following key for making certain tests to help differentiate genera
on the basis of color. Although it is a combination of characters which
differentiates algae in the final analysis, the key can select these char-
acters one by one only.

The three major phyla of algae (those which are the most com-
mon) are the green algae, the blue-green, and the yellow-green (yel-
low-brown). It is suggested that in order to facilitate the differentiation
of a green, a blue-green, and a yellow-green alga, that (if possible) a
known green alga (SpirogyraJ, a blue-green (Anabaena), and a diatom
(yellow-brown) be mounted on a microscope slide so that their color
and the details of cell structure might be compared. Then a series of
illustrations depicting these groups of the algae should be examined
so that the gross morphology and the details of cell structure will
become associated with the respective pigmentations.

HOW TO KNOW THE FRESH-WATER ALGAE

The phyla of freshwater algae herein recognized are as follows:

1 Chlorophyta (Green Algae).

Plants unicellular, colonial, or filamentous; swimming, floating, or
attached and stationary; cells containing plastids in which chlorophyll
(grass-green) is predominant, and in which there is usually a shiny,
starch-storing body, the pyrenoid; pigments are chlorophyll, xantho-
phyll, carotene; starch test with iodine positive (in almost every in-
stance); nucleus definite (although often small and inconspicuous); cell
wall usually relatively thick and definite, composed of cellulose and
pectose; swimming cells or motile reproductive elements furnished
with 2-4 flagella of equal length attached at the anterior end; sexual
reproduction by iso-, aniso- and by heterogametes.

2 Cyanophyta (Blue-Green Algae).

Plants unicellular, colonial, or in simple or branched (sometimes
falsely branched) filaments; without chloroplasts but with pigments in
solution and coloring the entire protoplast; variously colored with a
combination of chlorophyll, xanthophyll, carotene, phycocyanin, and
phycoerythrin; cell wall thin, a membrane which usually has a gela-
tinous outer sheath; contents often with false (pseudo-) vacuoles which
refract light and obscure the true color of the cells; definite nucleus
lacking but occurring as a cluster of granules in the mid-region (central
body) of the cell; motile cells and sexual reproduction wanting; asexual
reproduction by cell division (fission) or rarely by spores (akinetes);
food storage questionably glycogen, possibly floridean starch; iodine
test for starch negative.

3 Chrysophyta (Yellow-Green, or Yellow-Brown Algae).

Plants unicellular or colonial, rarely filamentous; pigments contained
in chromatophores in which yellow or brown often predominates,
chlorophyll, carotene and xanthophyll also present (some chromato-
phores appearing pale green or yellow-green); food storage in the
form of oil or leucosin, the latter often giving the cell a metallic lustre;
starch test with iodine negative; wall relatively thick and definite,
pectic in composition, often impregnated with silicon (especially in
the diatoms), and sometimes built in 2 sections which overlap in the
mid-region; motile cells and swimming reproductive cells furnished
with 2 flagella of unequal length, or with but a single flagellum; rhi-
zopodial (pseudopodial or amoeboid) extensions of the cell not uncom-
mon in some families.

4 Euglenophyta. (Euglenoids).

Cells solitary, swimming by one (usually) or by 2 (rarely 3) flagella;
a gullet present in the anterior end of the cell in many members, as is
also a red pigment (eye) spot; chloroplasts few to many variously
shaped green bodies (a few relatives colorless); a chlorophyll-like
pigment predominating, but with carotene also present; nucleus large

HOW TO KNOW THE FRESH-WATER ALGAE

and centrally located; food reserve in the form of an insoluble starch-
like substance, paramylum which is negative to the starch test with
iodine, and fatty substances; cell membrane in the form of a pellicle,
rigid or plastic, frequently striated; sexual reproduction unknown.

5 Cryptophyta (Cryptophyceae of some authors).

Cells solitary or colonial; mostly swimming by means of 2, often
laterally placed or sub-apical flagella; chromatophores large and
brown, or rarely blue, often with pyrenoids; food reserve in the form
of starch or oil; membrane firm but relatively thin; sexual reproduc-
tion unkown.

6 Pyrrhophyta. (Dinoflagellates).

Cells solitary or (rarely) filamentous; mostly swimming by means
of 2 flagella, one commonly wound about the cell in a transverse
furrow, and one extended posteriorly from the point of flagellar at-
tachment in a longitudinal furrow; cells dorsiventrally flattened and
differentiated, the longitudinal furrow extending along the ventral
surface; cell wall, if present, firm and often composed of regularly
arranged polygonal plates (as in the so-called armored or thecate
Dinoflagellates); pigments chlorophyll, carotene, four xanthophylls,
brown phycopyrrin, red peridinin (the latter sometimes predominating)
contained within chromatophores; food reserve starch or a starch-like
substance, and oil; a pigment (eye) spot often present; sexual repro-
duction unknown.

7 Rhodophyta. (Red Algae).

Plants simple or branched filaments (unicellular in one question-
able form); pigments contained within chromatophores, are chloro-
phyll, xanthophyll, carotene, phycocyanin and phycoerythrin, in the
freshwater forms appearing blue-green, gray-green, or violet (not red);
food reserve in the form of a special starch (floridean) which is nega-
tive to the iodine test for starch; walls relatively thick and often
mucilaginous, sometimes furnished with pores through which proto-
plasmic extensions occur; sexual reproduction by heterogametes, but
the male elements drifting and not swimming; thalli often of macro-
scopic size.

8 Chloromonadophyta (Chloromonads).

An obscure and little-understood group composed of but a few
genera and species; cells swimming, flagella one or two, apically at-
tached; chromatophores green, with chlorophyll (supposedly) predomi-
nating, but with an abundance of xanthophyll also present; food re-
serve in the form of oils or a fat; contractile vacuoles and a reservoir
in the anterior end of the cell; cell contents with trichocysts radiately
arranged just within the cell membrane (in the genus Gonyostomum),
sexual reproduction unknown.

8

HOW TO KNOW THE FRESH-WATER ALGAE

9 Phaeophyta. (Brown Algae).

A phylum mostly marine, including the brown sea weeds (kelps);
essentially filamentous (some microscopic) but mostly robust and leath-
ery; pigments include chlorophylls, carotene, xanthophyll, and fucoxan-
thin (predominating brown pigment); food reserve soluble carbohy-
drates including alcohol (mannitol); reproduction asexual by kidney-
shaped zoospores with 2 lateral flagella or sexual by iso- aniso- or
heterogametes.

SYNOPSIS OF THE ALGAL PHYLA

INCE many species and whole divisions of algae are prin-
cipally marine in habitat, the following general key or
synopsis is given as an aid to a better understanding of
the algal groups in fresh-water.

1 Cells without chloroplasts or chromatophores; pigments blue-green,
olive-green, or purplish, distributed throughout the entire protoplast
(although cells may be somewhat less colored in the central region);
wall usually thin (often showing as a membrane only) and gen-
erally with a mucilaginous sheath (wide or narrow, watery or firm
and definite); food reserve in the form of glycogen or a starch-like
substance; iodine test for starch negative; no motile cells present.
Blue-Green Algae CYANOPHYTA

1 Cells with chloroplasts or with chromatophores, the pigments not
distributed throughout the protoplast; cell wall clearly evident (with
rare exceptions PyTamimonas. see Fig. 30, e.g.); stored food not in
the form of glycogen; iodine test for starch positive or negative ... 2

2 Cells with grass-green chloroplasts (but see some species of Euglena.
see Fig. 8, or the filamentous alga, Trentepohlia, see Fig. 171 which,
although possessing chlorophyll, have the green color masked by
an abundance of the red pigment, haematochrome) 3

2 Cells with cholorplasts or chromatophores some other color, gray-
green, brown, violet-green, or yellow-green, sometimes purplish... 5

3 Free-swimming, unicellular; with numerous ovoid, star-shaped, or
plate-like chloroplasts which are grass-green; food stored as clearly
evident grains of insoluble paramylum (sticks, or plates); iodine
test for starch negative; one or two (rarely three) coarse flagella
attached at the apex in a gullet; eye-spot or red pigment spot usu-
ally evident Euglenoids EUGLENOPHYTA

3 Organisms not as above *

4 Unicellular, without an eye-spot; chloroplasts numerous discs usually
radially directed at the periphery of the cell; motile by means of 2
flagella inserted in an apical reservoir; trichocyst organelles usually
present just within the cell wall; food reserve oil

CHLOROMONADOPHYTA

4 Unicellular, colonial, or filamentous; swimming or not swimming
(although often free-floating); when swimming using 2 to 4 fine
flagella attached at the apex of the cell but not in a colorless reser-

10

HOW TO KNOW THE FRESH-WATER ALGAE

voir; chloroplasts 1 to several, usually with a conspicuous pyrenoid

(starch-storing granule); iodine test for starch positive

Green Algae CHLOROPHYTA

5 Chromatophores light olive-brown to dark brown; nearly all marine,
essentially filamentous, but occurring mostly as thalli of macro-
scopic size (brown sea weeds); stored food in the form of laminarin

and alcohol; starch test with iodine negative

Brown Algae . .PHAEOPHYTA

5 Plants marine or fresh-water, but not occurring as brown thalli of
macroscopic size 6

6 Chromatophores yellow-green to yellow- or golden-brown; food in
the form of leucosin or oil; starch test with iodine negative; plants
unicellular, colonial or filamentous; sometimes swimming with
apically attached flagella; many forms (especially the diatoms,

see Figs. 328-337) with the cell wall impregnated with silicon

Yellow-green Algae CHRYSOPHYTA

6 Chromatophores not yellow-green or pale green, but dark golden
brown, gray-green, violet-green; food in the form of oil or starch-
like carbohydrates; iodire test for starch mostly negative 7

7 Unicellular, with dark, golden-brown chromatophores; swimming by
means of 2 laterally attached flagella; a conspicuous eye-spot usu-
ally present; many forms with the cell wall composed of polygonal
plates Dinoflagellates PYRRHOPHYTA

7 Organisms unicellular or filamentous, not swimming by means of
laterally attached flagella; chromatophores brown, green, bluish,
violet-green or gray-green 8

8 Chromatophores violet or gray-green, sometimes bluish-green in
fresh water, red in marine forms; occurring as filamentous thalli of
both macroscopic and microscopic size; food stored in the form of

starch-like carbohydrates; starch test with iodine negative

Red Algae RHODOPHYTA

8 Chromatophores one or two golden-brown (rarely blue) bodies; or-
ganisms unicellular; swimming by means of sub-apically attached
flagella; food reserve in the form of starch-like carbohydrates; iodine
test positive in some CRYPTOPHYTA

(This class of the algae has several characteristics in common with
Dinoflagellates and in some systems of classification is included under
the Pyrrhophyta.)

11

HOW AND WHERE TO COLLECT FRESH-WATER

ALGAE

ILAMENTOUS algae can be collected from mass growths
by hand, of course, and representative tufts placed in vials
or collecting jars. Less conspicuous forms may be found
as fuzzy films on submerged grasses, old rush culms, and
sticks. Using the fingers these growths can be lifted away
or pulled from their attachment, or short sections of stems of aquatic
plants and grass leaves can be placed in vials and the algae removed
with scraping tools in the laboratory. A dropping pipette and a pair
of tweezers are useful for collecting minute forms.

Using the back of the thumb nail, or a dull-edged knife will serve,
greenish coatings on rocks and submerged wood can be scraped away.
Such an instrument is useful for removing samples of green or brown
felt-like or mucilaginous growths from wet stones about waterfalls,
from dripping cliffs and rocky outcrops.

Submerged glass, shells, and bits of crockery in the water furnish
substrates for many algae which occur as inconspicuous green discs
or tufts. Old, rotting wood may be perforated with algae which lie so
far below the surface that they are scarcely visible, but wood that
appears at all greenish from the exterior should be examined.

Feel under the rim of dams or along the edges of stones in flowing
water. Many blue-green and also some of the more rare freshwater
red algae occur in such habitats.

On and in damp soil are to be found numerous species of Cyano-
phyta and diatoms. Sometimes algae occur in pure strands' and sheets
or films of a single species may be lifted or scraped from soil, wet
boards, and the face of moist cliffs.

On beaches near the water line, but back far enough where the
sand lies unmolested most of the time, the upper dry layer of sand
may be removed to disclose a densely green stratum of algae. The
green sand can be scraped into a container and rinsed, and then when
the water is poured off in the laboratory an interesting mixture of
algae will be found, together with a variety of microscopic animals
(protozoa, rotifers, copepods, etc.). This biotic cosmos is known as
psammon and includes many organisms that normally occur in sandy
beaches although not in the open water of a nearby lake or stream.

In Nitella (one of the large green algae), in Lemna trisulca (one of
the duckweeds), in Bicciocarpus natans (a floating liverwort) occur vari-
ous green and blue-green endophytic algae. Small portions of these

12

HOW TO KNOW THE FRESH-WATER ALGAE

aquatic plants, and others as well, may be allowed to age and to be-
come discolored in dishes of water in the laboratory. The endophytes
(and some epiphytes too) will then appear more clearly and can be
dissected away for study.

In humid climates trunks of trees and surfaces of leaves may have
epiphytic or endophytic (semi-parasitic) algae such as Tientepohlia

The habitats of freshwater algae are very diverse, some
living in hot springs where the water is nearly at boiling
temperature; others in snow banks in high mountains;
whereas one alga normally occurs on the back of the
snapping turtle.

and Cephaleuios. Arisaema (Indian turnip) leaves invariably contain
the parasitic alga, Phylfasiphon, which causes yellow or red spots in
the host tissues.

One interesting habitat is the back of snapping turtles where the
coarse, wiry filamentous alga, Basicladia is invariably found. Other
algae may be associated with Basicladia on the 'mossy' backs of
turtles, whereas alligators are sometimes veritable algal gardens and
offer a variety of interesting forms for the less timid collector. In the
rain-forests of the tropics, Central America, e. g., the three-toed sloth
harbors among its hair scales a minute red alga, Cyanoderma hiady-
podis, and a filamentous green alga, Trichophilus welcheii.

In alpine and subalpine regions where there are banks of per-
manent snow, red streaks will be found at the margins of the snow
fields. The streaks are produced by the unicellular green alga, Chla-
mydomonas nivalis which contains a red pigment (haematochrome)
which is developed in the cells when they are exposed to intense

13

HOW TO KNOW THE FRESH-WATER ALGAE

light. A small quantity of red or 'bloody' snow when allowed to melt
in a jar may yield a surprising quantity of this and other genera
such as ScofieiJa, Ankistrodesmus, and certain Dinoflagellates.

Specimens collected
from the open water
(planktonic algae) are
best collected with a
cone-shaped, silk, bolt-
ing cloth net (No. 20).
Plankton nets are ob-
tainable from biologi-
cal supply houses, or
may be made up by
securing a yard of the
silk from an importer
or from a flour mill.

THE PLANKTON NET

(The Limnological and Oceanographic Society of America publishes
a list of commercial houses and firms where various kinds of col-
lecting equipment may be obtained.) A light-weight, brass (preferred)
or thin galvanized iron ring (stout wire), or band may be used for the
mouth of the net. A convenient size is a ring about 6 or 8 inches in
diameter. Using a pattern, (see Welch, P. S. 1948. Limnological
Methods, Blakiston Co., p. 234-235) cut the silk so that when attached
to the ring a cone about 14 inches long is formed. The silk should
not be attached directly to the ring, but sewed first to a band of stout
muslin which then may be sewed over the ring or metal band. If a
flat band is used for the mouth of the net the edges should be filed
smooth and rounded to eliminate as much cutting and fraying of the
muslin cloth as possible. The net may be used as a closed cone, in
which case after a sample has been collected, the net must be turned
inside out and the material washed off in a dish or jar. More con-
veniently, the tip of the cone may be cut off at a point (about Vi in.
or less from the end) which will permit the insertion of a small homeo-
pathic vial (4 to 6 dram capacity) which can be tied about its neck
into the apex of the net. Thus the sample will become concentrated
in the vial and when the net is reversed the material can be poured
out into a collecting bottle, and the net rinsed before another sample
is taken. Better still, a small metal (lightweight) band, threaded to
receive a screw-cap vial neck can be sewed into the tip of the net.
Then the vial can be simply unscrewed and a fresh one inserted after
the net has been rinsed.

The net should have 3 leaders of equal length attached to the
ring at regularly spaced points. The leaders should be tied to a
small ring to which the tow cord is also attached. Use a heavy line

14

HOW TO KNOW THE FRESH-WATER ALGAE

such as a stout chalk line for the pull cord and the leaders. Braided
copper wire is sometimes used for the leaders but these often become
so worn at the points of attachment that they snap.

Microscopic forms of algae may be obtained in great numbers
from the squeezing of Sphagnum (and other mosses) especially when
the plants feel slippery or slimy. Small pools and seeps in Sphagnum
beds abound in many species of algae, especially desmids. The moss
or overhanging dead grass and stems of rushes can be squeezed di-

Utricularia, an under-water animal-trapping plant, is a
veritable Christmas tree loaded with miscellaneous algae
which are caught among the leaves and held in the
mucilage that envelopes the plant.

rectly into a vial, or if a gross, mass collection is desired, the moss
can be squeezed into the plankton net so that a concentrated puree
of algae is obtained. Utricularia (bladderwort), especially when it oc-
curs in soft water or acid lakes, is a veritable net itself and handfuls
of this plant can be squeezed into a plankton net with very fruitful
results.

Specimens collected from the field should be put in receptacles
with just enough water to cover them, leaving ample space for air,
especially if the sample is to be stoppered for some time before arriv-
ing at the laboratory. Clots of larger, filamentous algae may have the
excess water gently squeezed from them, rolled in wet, and then in
dry paper (newspaper highly satisfactory) and so may be kept in
good condition for 24 hours or more.

Immediately upon returning from the field, vials or packets of
material should be opened and poured into wide, shallow dishes so
that they may be well aerated. If the collection is not too crowded
in a dish of water the plants may be kept alive and in good condi-

15

HOW TO KNOW THE FRESH-WATER ALGAE

tion almost indefinitely, especially if the dishes are stored in a cool
place with reduced iljumination such as in a north facing window.
Some kinds of algae Will remain in satisfactory condition for study
(even though additional growth may not occur) when stored in a re-
frigerator kept at ordinary temperatures used in food storage.

Some collectors prefer to spread algae on cards or stiff paper to
dry, and then made into herbarium specimens. In working with such
specimens later, a few drops of water placed on the dried plants will
soak up the material well enough that it can be lifted away for mount-
ing on a slide. Specimens so treated, however, are not satisfactory
for study unless one has had a long experience in examining algae
and is familiar with their appearance in the undried condition.

If it is desirable to keep a record of the location from which sepa-
rate field collections are made, it is obviously necessary to give sam-
ples a code number or label at the time they are taken. One satis-
factory way of doing this is to carry 3x5 inch cards, all but cut
through into narrow strips that will fit into the collecting vial. A num-
ber can then be written on a slip which is torn off from the card and
inserted. Information bearing the same code number can be written
into a field notebook for future reference. In the laboratory a per-
manent number can be assigned to the vial and written on the cork if
the material is to be saved for subsequent study.

PRESERVING
If samples are to be preserved an amount of 6-3-1 preservative
equal to the volume of the specimen (and its water medium) may be
added to the vial. This preservative is composed of six parts water, 3
parts 95% alcohol, and one part commercial formalin. If 5 cc of
glycerin are added to each 100 cc of the preservative, a medium is
produced which protects the specimen against total loss should the
preservative evaporate. Cork-stoppered vials, as a rule, are much
more serviceable than screw-cap vials which permit a greater amount
of evaporation of the liquid because the tops loosen upon standing for
a time.

Formalin-acetic acid-alcohol (FAA) makes an excellent preservative
and is especially suitable if material is later to be prepared for stain-
ing. To 50 cc of 95% alcohol add 5 cc of glacial acetic acid, 10
cc of commercial formalin, and 35 cc of water. Proprionic acid may
be substituted for the glacial acetic.

For general and incidental preserving, ordinary 3% formalin may
be used if the above ingredients are not available. (3 cc of com-
mercial formalin in 37 cc of water.)

If semipermanent microscopic mounts are desired, specimens may
be placed on a slide, evenly spread out, in a large drop of 5% glycerin.

16

HOW TO KNOW THE FRESH-WATER ALGAE

The slide should be set away under a dust-proof cover. Once or twice
a day for two or three days other drops of the glycerin solution are
added until, through evaporation of the water, approximately 100%
glycerin is obtained about the specimen. To this a small drop of melted
glycerin jelly is added and the cover slip put in place. Care should
be used to add just enough jelly to fill out the area under the cover
slip so as not to allow leakage from beneath it. The cover may then
be ringed with a sealing material such as balsam, colorless fingernail
polish, Bismark Black, or Gold Size. (See catalogues of biological
supply houses which list other kinds of mounting and sealing materials.)

17

A Selected List of Books and Major Papers Dealing
With the Classification of Fresh-water Algae

Atkinson, G. F. 1890. Monograph of the Lemaneaceae of the United
States. Ann. Bot., 4; 177-229. Pis. 7-9.

Boyer, C. S. 1916. Diatomaceae of Philadelphia and Vicinity. Phila-
delphia.

Brunnthaler, J. 1915. Protococcales. In: A. Pascher. Die Susswasser-
flora Deutschlands, Osterreichs und der Schweiz. Heft 5. Chloro-
phyceae 2: 52-205. Jena.

Chapman, V. J. 1941. An introduction to the study of algae. Mac-
millan Co., New York.

Collins, F. S. (1909) 1928. The green algae of North America. Tufts
College Studies, Sci. Ser. 2(1909); 79-480. Pis. 1-18. Reprinted with
supplements 1 and 2 by G. E. Stechert Co., New York, 1928.

Eddy, Samuel. 1930. The fresh-water armored or thecate Dinoflagel-
lates. Trans. Amer. Microsc. Soc, 49: 277-321. Pis. 28-35.

Elmore, C. J. 1921. The diatoms (Bacillarioideae) of Nebraska. Univ.
Nebr. Stud., 21(1/4): 1-214. 23 Pis.

Fritsch, F. E. 1935, 1945. The structure and reproduction of the algae.
I, II. Cambridge University Press.

Geitler, L. 1930-1931. Cyanophyceae. In: L. Rabenhorst, Kryptogam-
en-Flora von Deutschland, Osterreich und der Schweiz. 14 Lf.
1(1930): 1-288; Lf. 2(1931): 289-464. Figs. 1-131. Leipzig.

Gojdics. Mary. 1953. The Genus Euglena. Univ. Wisconsin Press.

Heering, W. 1914. Ulotrichlaes, Microsporales, Oedogoniales. In: A.
Pascher, Die Susswasserflora Deutschlands, Osterreich und der
Schweiz. Heft. 6, Chlorophyceae 3: 1-250. Figs. 1-384. Jena.

Irenee-Marie, Fr. 1939. Flore desmidiale de la region du Montreal.
547 pp. 69 Pis. La Prairie, Canada.

Jaques, H .E. 1948. Plant families — how to know them. Wm. C.
Brown Co., Dubuque, Iowa.

Krieger, W. 1933-1939. Die Desmidiaceen. In: L. Rabenhorst, Krypto-
gamen-Flora von Deutschland, Osterreich, und der Schwiez. 13
Abt. 1: 1-712. Pis. 1-96; Abt. 1, Teil 2: 1-117. Pis. 97-142. Leipzig.

Lemmermann, E. 1913. Euglenineae. Flagellatae 2. In: A. Pascher,
Die Susswasserflora Deutschlands, Osterreich, und der Schweiz.
Heft 2: 115-174. Figs. 181-377. Jena.

18

HOW TO KNOW THE FRESH-WATER ALGAE

Pascher, A. 1927. Volvocales-Phytomonadinae. In: Die Susswasser-
flora Deutschlands, Osterreich und der Schweiz. Heft 4: 1-506. Figs.
1-451. Jena.

Pascher, A. 1937-1939. Heterokonten. In: L. Rabenhorst, Kryptogamen-
Flora von Deutschland, Osterreich und der Schweiz. XI: 1-1097.
Figs. 1-912.

Prescott, G. W. 1927. The motile algae of Iowa. Univ. Iowa Stud.
Nat. Hist., 12: 1-4G. Pis. 1-10.

Prescott, G. W. 1931. Iowa algae. Iibd., 13: 1-235. Pis. 1-39.

Prescott, G. W. 1951. Algae of the Western Great Lakes Area. 933
pp. 136 Pis. Cranbrook Press.

Schiller, J. 1933-1937. Dinoflagellatae. In: L. Rabenhorst, Kryptogam-
en-Flora von Deutschland, Osterreich und der Schweiz. X(1933),
Teil 1: 1-617; Teil 2, Lf. 1(1935): 1-160; Lf. 2(1935): 161-320; Lf. 3(1937):
321-480; Lf. 4(1937): 481-590. Leipzig.

Smith, G. M. 1920, 1924. Phytoplankton of the inland lakes of Wis-
consin. I, II. Wis. Geol. Nat. Hist. Surv. Bull. 57. Madison.

Smith, G. M. 1950. Freshwater algae of the United States. 2nd Ed.
719 pp. 559 Figs. McGraw-Hill Book Co.

Tiffany, L. H. 1937. Oedogoniales, Oedogoniaceae. North American
Flora, 11, Part I. 102 pp. New York Botanical Garden.

Tiffany, L. H., and Britton, M. E. 1952. The algae of Illinois. 407 pp.
108 pis. Univ. Chicago Press.

Tilden, Josephine E. 1935. The algae and their life relations. 550 pp.
Figs. 1-257. Minneapolis.

Transeau, E. N 1951. The Zygnemataceae. Ohio State University
Press, Columbus, Ohio.

Wolle, F. 1887. Freshwater algae of the United States. Vols. 1, 2.
Bethlehem, Pa.

Wolle, F. 1892. Desmids of the United States and list of American
Pediastrums. Bethlehem, Pa.

19

PICTURED-KEYS TO THE COMMON GENERA
OF FRESH-WATER ALGAE

la Plants large (macroscopic), up to 40 or more cm. high, growing
erect, with stem-like whorled branches and iorked "leaves" clearly
visible to the unaided eye. Fig. 1-3 Family Characeae 2

lb Plants microscopic, or ii macroscopic with cellular structures and
branches not visible to the unaided eye, or scarcely so 4

2a Branching unsymmetrical, with dense heads oi short branches and
scraggly longer ones; microscopically showing globular antheridia
(male organs) lateral, beside the oval oogonia (female organs).
Fig. T TOLYPELLA

Fig. 1. Tolypella intricata (Trentep.) v.
Leonh. a, Portion of plant showing
habit of branching; b, a node show-
ing four oogonia and one antheridi-
um; c, an oogonium showing the
'crown' cells; d, tip of branch.

A rather rare plant in North America,
occurring in hard water lakes mostly.
It appears very much like Chara (Fig.
2) in need of a hair-cut but unlike Chora
it does not form dense beds in the bot-
tom of ponds and streams, but occurs
singly or in sparse clusters. Under the
hand lens Tolypella shows its true re-
lationship to Nitella (Fig. 3) in not hav-
ing column-like or fluting cells along
the stem and branches.

Figure 1

2b Branching symmetrical with rather evenly spaced whorls of equal-
length branches at nodes of the stem; antheridia above or below
the oogonia 3

'Some of the illustrations used in this volume have been redrawn from figures pre-
viously published by the author.

20

HOW TO KNOW THE FRESH-WATER ALGAE

3a Plants coarse and usually rough with lime; ill-smelling (garlic or
skunk odor); microscopically showing spherical antheridia lateral
and below the oval oogonia; branches with long, corticating colum-
nar cells about the main axial cell. Fig. 2 CHAR A

(Chara corona/a Ziz., however, has no corticating cells.)

Fig. 2a. Chara canescens Lois.-Des. A portion of a plant in which
thorn-like cells arising from the corticating elements give a spiny
appearance; b, one node of Chara excelsa Allen showing the oval
oogonium above, and the globular antheridium below.

Most of the species, of which there
are many, occurring in North America
are world-wide in their distribution.
They are to be found usually in streams
which are slow-flowing or in lakes in
which there is considerable calcium.
Some species especially are active in
depositing lime upon themselves and
are so harsh to the touch as to earn
the common name "stone-wort." Marl
and other kinds of calcareous deposits
may be formed largely by Chara over
long periods of time.

Figure 2

3b Plant delicate, or if relatively stout, not roughened with lime; dark
green, not ill-smelling; microscopically with globular antheridia
terminal on a short pedicel within a cluster of branches and above
the oogania; main axis not corticated. Fig. 3 NITELLA

Fig. 3a. Nitella tenuissima (Desv.) Kuetz., habit; b. Nitella ilexilis
(L.) C. A. Agardh, portion of plant showing habit of branching.

Species of Nitella are not seen
so often as are the Charas because
they usually grow more deeply,
thriving in soft water or acid lakes
rather than in hard water situa-
tions. Some species occur in bog
lakes that are darkly stained with
humic acids and are collected only
by dredging with a plant hook.
The plants are greener than Chara
and are not encrusted with lime;
are not ill-smelling.

Figure 3

21

HOW TO KNOW THE FRESH- WATER ALGAE

4a (1) Cells containing chloroplasts (bodies with green pigment pre-
dominating), or chromatophores (bodies with colors other than green

predominating) 5

4b Cells without chloroplasts and chromatophores, with pigments in
solution and more or less evenly diffused throughout the entire

protoplast Subdivision Myxophyceae 376

5a Plant grass- or leaf-green to gray-green; photosynthetic product
starch (iodine test positive), or paramylum (iodine test negative),
or floridean starch in the freshwater red algae which are greenish

or violet-green (iodine test negative) 6

Note: Because some Chlorophyta, or essentially green algae are
often tinged with red or yellow (the green color sometimes masked
by the other color), and because normally violet-green Rhodophyta
often appear green to the observer, the reader should compare plants
beipg keyed with:

No. 22a in the key, Haematococcus, a red unicellular, motile organism;
No. 60a in the key, Botiyococcus, colonial green alga in a brown,

nearly opaque mucilage;
No. 119a in the key, Rhodochytrium, a red unicell in the tissues of higher

plants.
No. 238a in the key, Trentepohlia, an orange-colored member of the

Chlorophyta.
No. 239a in the key, Batrachospermum, a filamentous member of the

Rhodophyta which is gray- or violet-green;
No. 256a in the key, Cephaleuros, a filamentous, semiparasitic and

nearly colorless member of the Chlorophyta;
No. 265a in the key; Leptosira, a yellowish-green filamentous mem-
ber of the Chlorophyta; and
No. 304a in the key, Botrydium, a green, balloon-like vesicle, belong-
ing to the Chrysophyta.

Also, see Trachelomonas, Fig. 5, identified by a brown shell which
incloses a green protoplast, and Dinobryon, Fig. 243, which has a color-
less, cone-shaped envelope (lorica) containing a protoplast which ap-
pears greenish.

5b Plant not grass- or leaf-green (but see Botrydium, Fig. 214, which
is green but belongs to the Chrysophyta (yellow-green algae); color
light green, violet-green, yellowish or brown; iodine test for starch

negative 283

6a Plants swimming in the vegetative state, solitary or colonial. (Pre-
served specimens should be examined for 2 or more minute pro-
tuberances at the anterior end of the cell which locate the position
of the flagella (organs of locomotion) that may have been retracted

or lost). Use 5% glycerine for mounts. See fig. 17 7

6b Plants not motile in the vegetative state; (check to be sure cell is
not a swimming organism at rest; see Trachelomonas, Fig. 5 which
although motile, is commonly found as a non-motile, brown shell
(lorica) from which the swimming protoplast has escaped); solitary,
colonial or filamentous 35

22

HOW TO KNOW THE FRESH-WATER ALGAE

7a Cells broadly ovoid or oval in outline, flattened as seen from the
side; chloroplasts radiately disposed at the periphery of the cell;

flagella 2, 1 trailing. Fig. 4. Division Chloromonadophyta

GONYOSTOMUM

Figure 4

Fig. 4. Gonyostomum semen (Ehr.) Stein,
showing numerous ovoid chloroplasts
and the radiately arranged "stinging"
organs. (Normally 1 flagellum is direct-
ed forward.)

This rare swimmer occurs mostly in acid bogs and in shallow lakes,
accompanying certain species of Euglena (See Fig. 8). Under the
microscope it reminds one of a flat, green bottle; usually is quiet in
the microscope fle'd so that its unique internal structure can be studied
easily. It has sudden, jerky movements for short distances.

7b Cells round or oval when seen in both front and side view, some-
times slightly flattened, but with flagella directed forward; chloro-
plasts not arranged as above; flagella 2, 4, 1 * 8

8a Cells with numerous, disc-like (rarely ribbon-like chloroplasts); food
reserve in the form of variously shaped, colorless or white para-
mylum bodies (See Fig. 6) which do not stain blue-black with
iodine; slow-moving by a stout flagellum (See Fig. 8); a red eye-
spot usually evident Division EUGLENOPHYTA 9

8b Cells with 1 cup-shaped or star-shaped chloroplast, usually con-
taining one or several conspicuous pyrenoids (doughnut-like, shiny
bodies buried in the chloroplast or on its surface); food reserve
starch, iodine test positive; lens-shaped eye-spot usually evident;
actively swimming with fine, often obscure flagella. (See Fig. 13).
(Add 5% glycerin to mount to slow down organisms for ob-
servation) 12

*Colorless, one-celled, swimming relatives of Euglena are not included here. Para-
menia and Astasia are examples of these strictly protozoan-like genera. Peranema has
one stout, rather rigid flagellum extended anteriorly, and a fine, inconspicuous one
oppressed close to the cell body. Astasia is highly plastic; swims by one flagellum;
has a prominent gullet in the anterior end.

23

HOW TO KNOW THE FRESH-WATER ALGAE

9a Cells inclosed in a brown shell (test), variously shaped, (round,
oval, or flask-shaped), often with a collar about the aperture through
which a single flagellum extends. (The variously shaped cells of
this genus frequently are found empty, yellow to dark brown,
smooth or decorated.) Fig. 5 TRACHELOMONAS

Fig. 5a. Trachelomonas granulosa Playf., a
short-collared species which has a warty
shell; b. Trachelomonas euchlora (Ehr.)
Lemm., protoplast within shell, showing eye-
spot, chloroplasts, and flagellum.

There are several hundred species of Tra-
chelomonas, each showing a differently
shaped shell, or lorica, and each having its
own special style of decoration. Usually the
loricas are found empty, brown, yellow, or
sometimes nearly colorless (determined by
the amount of iron present in the shell), intermingled with the mis-
cellaneous algae that grow in shallow water or bogs, or among weed
beds near the shores of lakes.

Figure 5

9b Cells not inclosed in a test

10

10a Cells flattened as seen from the side and often twisted; broadly
fusiform or nearly round in outline when seen from the front;
paramylum in the form of one to several 'doughnut' rings, or
discs. Fig. 6 PHACUS

Fig. 6a. Phacus curvicauda Swir., front
or ventral view showing eye-spot,
chloroplasts, and 2 ring-shaped para-
mylum bodies (food reserve); b, c,
Phacus triqueter (Ehr.) Duj. as seen
in end view, the triangular shape
being produced by the dorsal flange.

Although some species are spirally
twisted and 'top-shaped' most are flat
or at most are only slightly saucer-
shaped or pancake-like, with a long
or short tail-piece. The rings of stor-
age material are usually very con-
spicuous and so large as 'to fill nearly the entire diameter of the cell.

10b Cells not flattened, round in cross section; either elongate-fusi-
form or oval to round or somewhat pear-shaped in outline; para-
mylum bodies different from above 11

Figure 6

24

HOW TO KNOW THE FRESH-WATER ALGAE

11a Cells round, oval or pear-shaped, rigid, fixed in shape when
swimming; paramylum in the form of 2 large lateral rings; tail-
piece, if present, usually in the form of a short, sharp protrusion

from the rounded posterior end of the cell. Fig. 7

LEPOCINCL1S

Fig. 7a. Lepocinclis acuta Presc, showing
spiral markings of the periplast (mem-
brane); b, Lepocinclis glabra fa. minor
Presc, showing four lateral, band-like
paramylum bodies.

Round when seen on end, rather than
flat like Phacus (Fig. 6). The siorage ma-
terial in most species forms 2 rings that
lie along the side walls of the cell. Often
with Euglena (Fig. 8), but much more ac-
tive.

Figure 7

lib Cells often changing shape when swimming (rigid in some spe-
cies), elongate, nearly cylindrical, or fusiform; paramylum in the
form of a few and large, or numerous, small, colorless rods or
sticks; tail-piece formed by gradual narrowing of the cell. Fig. 8.
EUGLENA

Fig. 8a. Eugiena convoiufa Korsch.,
showing lateral paramylum plates as
seen on edge, one in flat view; b, E.
elastica Presc. Both of these are meta-
bolic species (changing shape while
in motion) whereas some forms are
rigid.

Although usually green, these elon-
gate, slowly moving species sometimes
are colored red because of a pigment,
haematochrome. A pond or slough may
have a bright red film over the surface
caused by Euglena which seem to pro-
duce the pigment in response to intense
light.

Figure 8

12a (8) Plant a colony of 4 or more cells, either closely adjoined, or free

from one another within a gelatinous envelope

Division CHLOROPHYTA (in the main) 13

12b Plant a solitary cell 22

25

HOW TO KNOW THE FRESH-WATER ALGAE

13a Cells arranged in a plane, forming a plate (flat or twisted) 14

13b Cells arranged to form a spherical, ovoid or spheroidal colony. .15

14a Colony horseshoe-shaped, flat or twisted. Fig. 9. . .PLATYDOR1NA

Fig. 9. Platydorina caudatum Kofoid. The fla-
gella of the organism in the center of the
colony are directed vertically to the surface.

Although rare this plant can be easily
identified by the flattened, slightly twisted,
horseshoe-shaped colony. It is to be found
in the same habitats with other members of
the Volvocaceae, Eudorina (Fig. 17), and Pan-
dorina (Fig. 14).

^oom<

u

\

*_■■'

Figure 9

14b Colony a circular or subquadrangular plate. Fig. 10. . . .GONIUM

A

' ,A £31 U;,

!^

Fig. 10. Gonium pecforaie Muell. An 18-
celled colony.

The number of cells in a colony may vary.
Other species (with cells shaped differently)
may have as few as 4 or as many as 32-64
individuals. The rectangular plates tumble
over and over as the colony swims through
the water.

Figure 10

15a Colony oblong or pear-shaped, with cells densely clustered and
all directed anteriorly, without an enveloping colonial mucilage. . 16

15b Colony globular or ovoid; cells inclosed in a mucilaginous sheath,
but not all directed one way 18

26

HOW TO KNOW THE FRESH-WATER ALGAE

16a Colonies small (2-4 cells). Fig. 11 PASCHER1ELLA

Figure 1 1

Fig. 11. Pascheriella tetias Korsch. Cells showing
eye-spot (lateral) and subflagellar vacuoles at
the apex.

Rare. Is to be looked for in small rain water
pools and catch basins of temporary duration.

16b Colonies of 8-16 cells 17

17a Cells with 4 flagella, arising from a protuberance at the broad
end. Fig. 12 SPONDYLOMORUM

Fig. 12. SpondyJomorum quaternarium Ehr.
a, colony; b. single organism showing
posterior eye-spot and subflagellar va-
cuoles.

Pear-shaped cells huddled together with
their broad ends all directed the same
way; eye-spot is posterior rather than an-
terior as in most of its relatives. The 4
flagella are difficult of determination ex-
cept under favorable optical conditions.

Figure 12

17b Cells with 2 flagella. Fig. 13 CHLAMYDOBOTRYS

Fig. 13. Chlaitiydobotrys gracilis Korsch. A col-
ony of individuals with posterior eye-spots.

Like Spondylomorum (Fig. 12) cells of this
colonial organism are closely grouped; have
2 long flagella and a conspicuous eye-spot.

Figure 1 3

27

HOW TO KNOW THE FRESH-WATER ALGAE

18a (15) — Colony spheroidal or oval; cells pear-shaped, crowded to-
gether with broad ends all directed outwardly. Fig. 14

PANDORINA

Fig. 14. Pandoiina morum Bory. Cells are
pear-shaped and often are more compact-
ly arranged than shown here.

A tumbling colony in which pear-shaped
cells are closely compacted within a spher-
oidal or oval gelatinous sheath. Often col-
onies are to be seen in which all individuals
have divided to form each a daughter colony.
There is one other species in the United
States, (possibly a Eudorina Fig. 17).

Figure 14

18b Colony globular or broadly ovoid; cells not crowded but evenly
spaced (even though close together) 19

19a Colonies large, containing hundreds or thousands of cells. Fig.
15 VOLVOX

Figure 15

Fig. 15. Volvox tertius Meyen. a. Colony
showing only vegetative cells; b, two
organisms showing eye-spot. Other
species have colonies containing a
larger number of cells, and some have
intercellular connections.

This globular colony containing thou-
sands of cells is usually easily seen
with the unaided eye. It occurs in water
that is rich in nitrogenous substances
(frequently) and sometimes causes
"blooms" of short duration (two or three
days during summer months).

19b Colonies composed of 8-16-64-128 cells

20

28

HOW TO KNOW THE FRESH-WATER ALGAE

20a Cells fusiform with sharply pointed lateral processes or extensions
of the protoplast. Fig. 16 STEPHANOSPHAERA

Fig. 16. Stephanosphaera pluvi-
alis Cohn. Oval colony with
organisms forming a median
band. The cells commonly
show 2 pyrenoids (starch-
storing bodies).

Like Pascheriella (Fig. 11) this
plant occurs in small, tempo-
rary pools; is easily identified
by its irregularly shaped cells
forming a transverse belt in a
compressed, spheroidal gelatin-
ous sheath.

Figure 16

20b Cells round or ovoid, without lateral processes 21

21a Cells all the same size within the colony. Fig. 17 EUDORINA

Figure 17

Fig. 17. Eudorina elegans Ehr.
In this species the cells have
a tendency to arrange them-
selves in transverse bands or
tiers. Occurs along with
Volvox (Fig. 15) and Pleo-
dorina (Fig. 18).

Unlike Pandorina (Fig. 14) the
cells are round or oval and
rather evenly spaced within
the colonial mucilage. Eudo-
rina unicocca G. M. Smith is
another species which has been
reported from the United States,
differentiated by the colony
showing a slight polarity with
the sheath forming lobes at the
posterior end.

29

HOW TO KNOW THE FRESH-WATER ALGAE

21b Cells of 2 sizes within the same colony, the smaller arranged at
one pole of the envelope. Fig. 18 PLEODORINA

Fig. 18. Pleodorina illinoisensis Kofoid.
Another common species (P. califoi-
nica Shaw) has about one-half of the
cells larger and with reproductive
capacity, the smaller cells being
strictly vegetative.

®k<

Colonies are perfectly spherical like
most Volvox (Fig. 15) but have many
fewer cells (usually 128). Although PJeo-
dorina often occurs in the same habitat

with Voivox it can be distinguished quickly by the two sizes of cells

in the colony.

Figure 18

22a (12) — Protoplast at a considerable distance within the cell wall
and connected to it by fine, radiating processes; cells with a mass
of red pigment often present in the center of the protoplast (some-
times masking the green color); usually encysted, forming rust-
colored encrusting growths in bird baths and cemented pools.
Fig. 19 HAEMATOCOCCUS

Fig. 19. Haematococcus lacustris (Girod.)
Rostaf. a, swimming cell showing pro-
toplast with radiating processes; b,
cysts (which usually are brick-red in
color).

The wide gelatinous wall with fibrils
of protoplasm extending out from the
cell membrane identify this motile or-
ganism. It is widely distributed and a
common inhabitor of garden pools and
catch basins in rocks.

Figure 19

22b Cells not as above; free-swimming 23

23a Cells with a definite (although sometimes thin) wall, often with a
gelatinous sheath 24

23b Cells without a definite wall; chloroplasts lying against the cell
membrane; gelatinous sheath wanting 32

30

HOW TO KNOW THE FRESH-WATER ALGAE
24a Cells with 4 flagella 25

24b Cells with 2 flagella 26

25a Cells flattened when seen from the side or from the top. Fig. 20.
PLATYMONAS

Fig. 20. Platymonas elliptica G.
drawn from Smith.)

M. Smith. (Re-

Although usually found in brackish water, this
genus contains at least one species that appears
in freshwater. To make identification the cells
should be seen from the top or side to determine
whether they are flattened.

Figure 20

25b Cells round when seen from the side or from the top. Fig. 21.. . .
CARTERIA

Fig. 21a. Carteria cordiformis (Carter) Dies.;
b, Carteria *Klebsii Dill.

Like Platymonas (Fig. 20) this genus is
characterized by having four flagella but the
cells are round when seen in end view. The
chloroplast is variable in shape and may not
appear as shown in the illustration. It may
be a thin plate along the wall, cup-shaped
and covering most of the wall except at the
anterior end, or H-shaped.

Figure 21

26a Cell wall with lateral, wing-like margins or flanges

27

31

HOW TO KNOW THE FRESH-WATER ALGAE

26b Cell wall smooth, without flanges

29

27a- Envelope roughened or warty, the flanges forming 4 lobe-like ex-
tensions when seen from the top or side. Fig. 22

WISLOUCHIELLA

Fig. 22. Wislouchiella planctonica Skvor. a,
'front' view; b, side view.

Named for the biologist Wislouch, this bi-
flagellated organism is identified quickly by
the oddly-shaped lobes or processes of the
wall which extend in several planes. Rare.

Figure 22

27b Envelope not roughened, or if roughened, without lobe-like ex-
tensions 28

28a Envelope composed of 2 overlapping pieces, the seam showing
when the vegetative cell is seen from the side. Fig. 23.

PHACOTUS

Figure 23

Fig. 23. Phacotus lenticularis (Ehr.) Stein.
a. 'front' view; b, side view showing bi-
valve structure of cell wall.

This genus is relatively rare, but is often
abundant in collections from habitats where
it occurs. It is both euplanktonic (a true
plankter) and tychoplanktonic and may oc-
cur in river as well as in lake collections.

32

HOW TO KNOW THE FRESH-WATER ALGAE

28b Envelope with 2 overlapping sections which do not show except
when the cell is in the process of dividing; envelope 4-angled when
seen from the 'front.' Fig 24 PTEROMONAS

Fig. 24. Pteromonas aculeata Lemm.

This genus takes its name from the winged
appearance of the envelope. Although there
are about 7 species known, the most common
perhaps is Pteromonas aculeata Lemm. recog-
nizable by the rectangular appearance as seen
in 'front' view. Like Phacotus (Fig. 23) this spe-
cies sometimes occurs in the plankton of rivers.
See Scotiella (Fig. 127), a genus which has been
regarded by Pascher as belonging to Pteromo-
nas.

Figure 24

29a (26) Cells elongate or fusiform. Fig. 25 CHLOROGON1UM

Fig. 25. Chiorogonium sp.

Of the 8 species known for this genus only 2 are
reported from the United States. They are all more
elongate than any other members of the order Volvo-
cales. Usually found in swamps and shallow ponds,
they sometimes appear abundantly in laboratory
aguaria.

Figure 25
29b Cells round, oval or angular

30

30a Cell wall with lump-like protuberances or short lobes. Fig. 26

LOBOMONAS

Fig. 26. Lobomonas rostrata Hazen.

The irregular lumpy appearance of this genus is
its chief characteristic. The organisms appear in the
same habitat with Haemafococcus (Fig. 19), i.e., tem-
porary rain water pools and cement basins.

Figure 26

33

HOW TO KNOW THE FRESH-WATER ALGAE

30b Cell wall without protuberances

31

31a Gelatinous envelopes shaped similarly to the protoplasts. Fig. 27.

CHLAMYDOMONAS

Fig. 27a. Chlamydomonas polypyrenoi-
deum Presc; b, Chlamydomonas
sphagnicola Fritsch & Takeda, a spe-
cies with bipapillate protrusions at
the anterior end of the sheath.

Whereas this common genus is repre-
sented by approximately 175 described
species, it is doubtful that they are all
distinct. Unless specimens are given
careful study they may be confused
with other minute biflagellate green
cells belonging to other genera, or with
zoospores. Variations of the same spe-
cies may be described under different names. The species of this genus
are encountered more frequently than any other members of the Volvo-
cales and are to be found in a great variety of habitats, from the plank-
ton of lakes to the green water of rain barrels. A favorable place for
them is the barnyard pool or watering trough. C. nivalis (Bauer) Wille
produces red snow at high altitudes.

Figure 27

31b Gelatinous envelope and protoplast different in shape from one
another. Fig. 28 SPHAERELLOPS1S

Fig. 28. Sphaerellopsis fluviatilis Pascher.

This genus probably should be classi-
fied under Chlamydomonas although spe-
cialists separate its 2 species on the basis
of the very wide gelatinous sheath be-
ing different in shape from that of the
protoplast. It occurs in the tychoplanktor
of small lakes, and in pools.

Figure 28

34

HOW TO KNOW THE FRESH-WATER ALGAE

32a (23)— Flagella 6-8. Fig. 29 POLYBLEPHAR1DES

Fig. 29. Polyblepharides fragariitormis Hazen, showing
3 of the 4 contractile vacuoles at the anterior end.
(Redrawn from Hazen.)

Apparently there are only 2 species on record for this
genus. They possess 6-8 flagella and several contractile
vacuoles at the anterior end.

Figure 29

32b Flagella 2-4 33

33a Flagella 2 34

33b Flagella 4. Fig. 30 PYRAMIMONAS

Fig. 30. Pyramimonas tetrarhynchus Schmar. a,
'front' view; b, end view showing points of
attachment of the flagella.

This is Pyramidomonas of some authors; con-
tains at least 8 species all of which are 4-lobed
when seen in end view, with a flagellum at-
tached in each of the four depressions between
th'3 lobes.

Figure 30

34a Cells ovoid but with lobes or flanges, appearing 6-angled when
seen in end view. Fig. 31 STEPHANOPTERA

Figure 31

Fig. 31. Stephanoptera gracilis (Ar-
^tari) G. M. Smith, a, 'front' view;
b, end view, showing point of
attachment of flagella.

This genus takes its name from the
fact that it is crown-shaped or 6-
lobed when seen on end; the flagel-
la being centrally attached in the
anterior end.

35

HOW TO KNOW THE FRESH-WATER ALGAE
34b Cells oblong or ovoid, without lobes. Fig. 32 DUNALIELLA

Fig. 32. Dunaliella salina Teodor. Two differently-
shaped individuals.

This species and D. viridis Teodor. are appar-
ently the only ones described thus far for the
genus, but they are widely distributed judging
from reports of them in different parts of the
world, occurring in brackish or saline waters.

Figure 32

35a (6). Plant a filament (cells in continuous or interrupted series)
with or without branches; or a flat expanse or attached cushion
with the branches closely oppressed so that the basic filamentous
plan is not clearly evident; or a tubular, thread-like thallus without
cross walls (coenocytic) 189

35b Plants not filamentous, but solitary cells or a colony of 2 or more
cells inclosed by mucilage or by an old mother cell wall (see Oocy-
stis. Fig. 85), or cells variously adjoined to one another (Scenedes-
mus. Fig. 74; Pediastrum, Fig. 70) 36

36a Cells solitary or gregarious but not adjoined to form colonies. .109

36b Cells adjoined or arranged in colonies

37

37a Colony composed of 2 trapezoidal cells adjoined along their broad
bases. Fig. 33 EUASTROPS1S

Figure 33

Fig. 33. Euastropsis Richteri (Schmid.) Lag.

This is the only species of the genus on rec-
ord. The two cells which compose the colony
appear much like those of Pediastrum (Fig. 70)
but are never more than this number joined
together. Euastropsis occurs in the tychoplank-
ton; is rare but widely distributed.

36

HOW TO KNOW THE FRESH-WATER ALGAE
37b Colony composed otherwise 38

38a Colony composed of cells invested by a common mucilage (see
Oocysfis, Fig. 85b, with cells inclosed by old, expanded mother cell
wall, not by mucilage) 39

38b Colony composed of an aggregate of cells not inclosed by mu-
cilage, but may be inclosed by old mother cell wall or fragments
of it 73

39a Colony attached or adherent 40

39b Colony free-floating or entangled among other algae, but not grow-
ing attached (frequently algae usually attached become separated
from their substrate. Look for attaching stalk, disc or other evi-
dence of the plant having been once attached) 49

40a Colonies in the form of compact packets among the epidermal
cells of aquatic plants. Fig. 34 CHLOROSARCINA

Fig. 34. Chlorosarcina consociata (Klebs).G.
....^=^ M. Smith.

>^§>^^y •Tv^C^- ^ is P ac ^ et_n ^ e arrangement of cells is re-

*C?jfrQS$$\j#&pQ} min dful of the genus Sarcina among the bac-

i(7)A^^^^^^^' teria - There are 3 species, usually free-living

;^jvA! ; but one that is most frequently seen occurs

V^J/^/Ta in the tissues of such aquatic plants as Lemna.

^(jL^y Old, colorless specimens of Lemna often show

this and other endophytic algae {Chlorochy-

Figure 34 trium Lemnae, Fig. 94).

40b Colonies not endophytic in the tissues of aquatic plants 41

41a Colonial mucilage sac-like, balloon-shaped or intestiniform, often
macroscopic 42

41b Colonial mucilage of other shapes, or if sac-like, microscopic .. 43

37

HOW TO KNOW THE FRESH-WATER ALGAE

42a Aquatic; cells without individual sheaths definitely arranged in
4's (or sometimes in 2's) mostly at the periphery of the common
mucilage; under favorable optical conditions often showing long,
fine, hair-like extensions (pseudocilia or false flagella). Fig. 35.
TETRASPORA

Fig. 35a. Tetiaspoia cylindiica (Wahl.) C. A.
Agardh, habit of colony; b, Tetraspoia gela-
tinosa (Vauch.) Desvaux, habit of colony; c,
arrangement of Tetraspora cells; d, single cell
showing cup-shaped chloroplast.

Early in the spring or throughout the summer
in cold running water gelatinous, balloon-like or
intestiniform strands of Tetraspora may be found
attached to stones or to gravel, sometimes build-
ing masses 2 or 3 feet in length. Most of the
dozen or so recognizable species are macrosco-
pic but a few appear as microscopic, floating
thalli. When the colonies are young and if care
is used in obtaining ideal optical conditions, the
long fine (often shadowy) pseudocilia are dis-
cernible.

Figure 35

42b Terrestrial (usually); cells sometimes with indistinct sheaths, not

definitely arranged in 4's; without pseudocilia. Fig. 36

PALMELLA

} Fig. 36. Palmella miniata Liebl. a,
habit of colony; b, portion of col-
ony showing arrangement of cells
and individual cellular sheaths.

This plant forms lumpy gelatin-
Figure 36 ous masses, 2-8 or more millimeters

in diameter on damp soil or on rocks,
especially about water falls. The cells of P. miniata are often red
with the pigment haematochrome, whereas P. mucosa (without indi-
vidual cellular sheaths of mucilage) is always green.

38

HOW TO KNOW THE FRESH-WATER ALGAE

43a (41) Colony balloon-like or pear-shaped, narrowed at base to form
a stalk-like attachment; pseudocilia usually visible. Fig. 37....

APIOOYSTIS

■OqOo °° tr -

'b 00 od °°
",8 % °V

o o'a-"

,4>.-- .

" °o °„ o oo °°*

,MDO

00 - o

oo- .

;*.

°.

S

j'oO 00 9j> „" "*<4

:■/» ooo o cb

>°° o

o oo Op..

e% a *■> «. w i

'%*> 8 *«?>>'

..•V y»„ <

/v o<5.

\o o O „

<? OO o ,•

Fig. 37. Apiocystis Brauniana Naeg. Dia-
gram of a colony showing cell arrange-
ment and pseudocilia.

This plant is always in the form of a micro-
scopic thallus growing attached to filamentous
algae or to stems of aguatic plants. The
cells are arranged somewhat irregularly in
four's and under favorable conditions show
pseudocilia like Tetiaspoia. (Fig. 35.)

Figure 37

43b Colony some other shape; pseudocilia absent 44

44a Colonial mucilage forming a fusiform shaped envelope; cells simi-
larly shaped as the envelope, with long axes more or less parallel.
Fig. 38 ELAKATOTHRIX

Fig. 38.
Printz.

Elakatothrix viridis (Snow)

Somewhat 'cigar'-shaped cells placed
end to end in pairs within a fusiform,
gelatinous sheath. E. gelatinosa Wille
has both ends of the cell pointed where-
as other species have the adjoined
,Qure poles truncate. In one of the three

species found in this country, Elakatothrix americana Wille, the gela-
tinous colonial sheath is irregularly lacy or fringed.

44b Colonial mucilage not fusiform 45

39

HOW TO KNOW THE FRESH-WATER ALGAE

45a Cells cylindrical or elongate-ovoid, scattered throughout amorphous
mucUage. Fig. 39 COCCOMYXA

Fig. 39. Coccomyxa dispar Schmidle, cells in
the tips of gelatinous strands.

There are three recorded species of this
genus but only Coccomyxa dispar Schm.
seems to have been found in this country,
forming gelatinous masses of varying extent
on damp soil, on wet wood, or more rarely
free-floating. It has been found attached in a
wooden flume of swiftly flowing water.

Figure 39

45b Cells shaped otherwise 46

46a Cells elliptical or nearly spherical, arranged in 2's and 4's within
ungelatinized walls of mother-cell; pigment spot (eye-spot) usually
evident. Fig. 40 .... PALMELLA— STAGE OF CHLAMYDOMONAS

Fig. 40. Palmella-stage of Chlamydo-
monas.

Chlamydomonas (Fig. 27) often be-
comes quiescent in unfavorable habi-
tats, or as a normal stage in its life
history. The cells adhere to a substrate,
lose their flagella, but continue to di-
vide, sometimes forming extensive gela-
tinous masses. The cells are arranged
Figure 40 in 2's or 4's and are surrounded by

mucilaginous sheaths, thus somewhat re-
sembling Palmella (Fig. 36). In this form Chlamydomonas is often
mistaken for Gloeocystis (Fig. 41). Laboratory aquaria often contain
Chlamydomonas in this stage. The cells may become actively motile
again by developing new flagella.

46b Cells spherical (sometimes oval) irregularly scattered throughout
mucilage; orange-colored oil globules sometimes present; red eye-
spot lacking 47

40

HOW TO KNOW THE FRESH-WATER ALGAE

47a Cells inclosed by concentric layers of mucilage (individual cell
sheaths distinct). Fig. 41 GLOEOCYST1S

. $

b v

/

&

\

•

-

°^

Figure 41

Fig. 41a. Gloeocystis gigas (Kuetz.) Lag.; h.Gloeocystis ampla (Kuetz.)
Lag.; a Gloeocystis major Gerneck, showing dense, cup-shaped
chloroplast.

There are several species of Gloeocystis and all are very common.
They are not very distinctive plants and therefore many small, round
green cells, especially when inclosed in mucilage, belonging to other
genera may be mistaken for them. The concentric layers of mucilage
about the cells provide a helpful character for identification. Gioeo-
cystis ampla (Kuetz.) Lag. does not have layers of mucilage, however,
but this free-floating species is identified by its oblong or oval cells.

47b Cells without evident individual sheaths; mucilage not in con-
centric layers 48

48a Chloroplast cup-shaped, not covering the entire wall; cells all the
same size within the colonial mucilage. See Fig. 36. . .PALMELLA

This genus has shapeless lumps of attached mucilage, sometimes
large enough to be seen easily with the unaided eye. The oval cells
scattered throughout the mucilage may have individual sheaths. Like
Gloeocystis (which also has cup-shaped chloroplasts, Fig. 41) other
small, oval cells may be mistaken for Palmella and vice versa.

41

HOW TO KNOW THE FRESH-WATER ALGAE

48b Chloroplast covering almost the entire wall; cells variable in size
within the colonial mucilage. Fig. 42 CHLOROCOCCUM

Fig. 42. Chlorococcum humicola (Naeg.) Rab. Cells
occasionally are seen to be inclosed in a mucila-
ginous sheath.

Although this plant occurs on soil it reproduces
by swimming reproductive cells (zoospores). An-
other species, Chlorococcum infusionum (Schrank)
Menegh. is aquatic and is differentiated from C.
humicola by the fact that its cells are all uniform
Figure 42 in size and shape. Old, wet bones, and rocks un-

der dripping water are favorable places for both
species. Unless it is Pieurococcus CProfococcusJ, Fig. 66, Chlorococcum
humicola is probably the most widely distributed algal species in the
world.

49a (39) — Colony fusiform, definite in shape. See Fig. 38

ELAKATOTHRIX

49b Colony not fusiform, but cubical, globular quadrate, or irregular
in shape 50

50a Colony regularly spherical, oval, or a rectangular plate

61

50b Colony irregular or some other shape (but young stages of Tetra-
spora. (Fig. 35), may be somewhat spherical) 51

51a Colony of 4 cells in one plane interconnected by strands, the cells

bearing a scale-like fragment of mother-cell wall. Fig. 43

CORONASTRUM

Fig. 43. Coronastrum aestivale Thompson.
(Redrawn from Thompson.)

This is a very rare alga and the only one
of three species in the genus which has been
reported from America. The arrangement
of the cells and their distinctive wing-like
scale make it easy of identification.

Figure 43

42

HOW TO KNOW THE FRESH-WATER ALGAE

51b Colony formed otherwise

52

52a Colony cubical, consisting of 4 cells at the corners of a hollow
cube built of gelatinous strands. Fig. 44 PECTODICTYON

Figure 44

Fig. 44. Pectodictyon cubicum Taft.
drawn from Taft.)

(Re-

There is only one species known for this
genus and it has been found but once since
it was originally described by Taft from
Ohio. It is to be expected in open water
plankton.

52b Colony formed otherwise 53

53a Cells arranged in a linear series within gelatinous tubes (often
branched). Fig. 45 PALMODICTYON

© © © Q Q<

Figure 45

Fig. 45. Palmodictyon viride Kuetzing.

This species and Palmodictyon varium (Naeg.) Lemm. are fairly
common in mixtures of algae from the shallow water of ponds and
swamps. The former has cells inclosed in individual sheaths, whereas
the latter is without cellular sheaths. Some strands of colonial muci-
lage may be simple, others irregularly branched and sometimes ana-
stomosing.

53b Cells arranged otherwise 54

54a Cells cylindrical or elongate-ellipsoid 55

43

HOW TO KNOW THE FRESH-WATER ALGAE
54b Cells other shapes 56

55a Chloroplast axial with one to several pyrenoids. Fig. 46

MESOTAEN1UM

Figure 46

Fig. 46. Mesotaenium Greyii Turner (forma), show-
ing variation in cell shape.

These oval or oblong cells have an axial, plate-
like chloroplast and a wall that is all in one piece
(Saccoderm desmids). Although some of the 5 or 6
species occurring in the country are free-floating,
others (Mesotaenium macrococcum (Kuetz.) Roy and
Biss., e.g.) usually occur among mosses and in vari-
ous swamp situations. In high mountain seeps they
may occur as gelatinous masses on rocks.

55b Chloroplast a parietal plate, without a pyrenoid. See Fig. 39

COCCOMYXA

56a Colony forming stringy, intestiniiorm masses, sometimes perfor-
ated skeins. See Fig. 35a TETRASPORA

56b Colony shaped otherwise 57

57a Colony a few (2-4) oval cells inclosed in an irregularly shaped,
layered, gelatinous sheath. Fig. 47 DACTYLOTHECE

'.

Figure 47

Fig. 47. Dactylothece sp.

Cells in this genus are shaped as in Mesotae-
nium (Fig. 46) but they are much smaller (not more
\ than 3 p in diameter) and have a laminate, pari-
etal chloroplast. The cells are inclosed in mu-
cilage and form thin expanded masses on moist
rocks. D. confluens (Kuetz.) Hansg. is the only
species reported from North America.

44

HOW TO KNOW THE FRESH-WATER ALGAE

57b Colony composed of round or oval cells, gelatinous sheath not
stratified 58

58a Semicircular fragments of old mother-cells partly inclosing daugh-
ter cells or lying scattered about in the mucilage. Fig. 48

SCHIZOCHLAMYS

Fig. 48. Schizochlamys geia-
tinosa A. Braun.

At times the free-floating
gelatinous masses of this
plant may be of macroscopic
size and they may be
scooped from the surface of
the water by hand. More
Figure 48 frequently the growths are

less extensive and small aggregates of cells occur intermingled with
other algae in shallow water situations. The fragments of old mother-
cell walls help to identify this plant, and under favorable optical con-
ditions the tuft of fine, gelatinous pseudocilia may be seen.

58b Fragments of old mother-cell walls not apparent 59

59a Colonies sac-like or irregularly globose; cells arranged in 4's. See
Fig. 35b TETRASPORA

59b Colonies shaped otherwise; cells not arranged in 4's 60

60a Cells ovoid, compactly arranged in semi-opaque mucilage which
is often brown or yellow and obscures the cells; colonies frequent-
ly compounded by interconnecting strands of tough mucilage be-
tween clusters of cells. Fig. 49 BOTRYOCOCCUS

Fig. 49. Botryococcus Biaunii Kuetz.,
showing an expression in which a
colonial complex is formed by inter-
connecting strands of tough mucil-
age. Colonies frequently appear
solitary and as a yellowish-brown
lump in which individual cells can
scarcely be seen, if at all. The
color of the colony lies mostly in
the mucilage. This species often
forms "blooms" especially in hard
water lakes.

Figure 49

45

HOW TO KNOW THE FRESH- WATER ALGAE

60b Cells round or oval, not arranged in semi-opaque mucilage. See
Fig. 41b GLOEOCYST1S

61a (50) Cells incised or constricted in the mid-region to form 'semi-
cells', the cells often interconnected by fine gelatinous strands. Fig.
50 COSMOCLADJUM

GO © ,

Fig. 50. Cosmocladium tuberculatum Presc.

This species has every appearance of a tiny
Cosmarium-like desmid (Fig. 113) in which the
cells are enveloped in a colorless, gelatinous
sheath. There are but few species in the genus,
occurring with other desmids in soft water or
acid bogs. Under favorable optical conditions
the fine intercellular connecting strands of mu-
cilage can be determined.

Figure 50

61b Cells not constricted to form 'semi-cells'

62

62a Chloroplast star-shaped, the radiating processes with their outer
ends flattened against the wall. Fig. 51 ASTEROCOCCUS

Fig. 51. Asterococcus superbus
(Cienk.) Scherf.

This species and A. limneticus
G. M. Smith are the only ones
known to occur in North America.
A. superbus may occur singly or
in colonies of 2 or 4 cells and
Figure 51 shows the star-shaped chloroplast

more clearly than does the former
which has smaller cells, 8 to 12, rarely 16 in number within a common
envelope. A. limneticus, as the name suggests, is found in open water
plankton.

62b Chloroplast not star-shaped

63

46

HOW TO KNOW THE FRESH-WATER ALGAE

63a Cells arranged in groups of 4's at the ends of branching mucila-
ginous strands (focus carefully into the colony). See Fig. 52 .... 64

63b Cells not arranged at the ends of branching strands 65

64a Cells appearing both reniform (sausage-shaped) and ovoid in the
came colony. Fig. 52 D1MORPHOCOCCUS

Fig. 52. Dimorphococcus lunatus A. Braun.

In this plant the cells are in clusters of 4, 2 of
which when seen in 'top' view appear oval,
whereas the others, seen from the side, appear
bean-shaped or somewhat crescent - shaped,
hence the species name. Dimorphococcus luna-
tus is often abundant in soft water lakes, where-
as the other species known from this country,
D. cordatus Wolle, is less frequently found.
Both species may occur in open water plankton
or in the tychoplankton near shore. A char-
acter that is helpful in identification is a negative one, the absence of a
conspicuous gelatinous sheath inclosing the colony.

Figure 52

64b Cells spherical or broadly oval, all the same shape within the
colony. Fig. 53 D1CTYOSPHAERIUM

Fig. 53. Dictyosphaerium pulchel-
lum Wood, a, Habit of colony;
b, Individual cells at ends of
radiating strands.

Cells are in clusters of 4, as in
Dimorphococcus (Fig. 52) but all
the same shape, round or oval,
smaller in size and often more
numerous in the colony which is
invested by a colonial mucilage.
The radiating, branched thread-

Figure 53

like strands are the remains of the old mother-cell wall which has
broken down to release daughter-cells.

65a Cells globular 66

65b Cells other shapes, ovoid, fusiform, crescent-shaped, or bean-
shaped 68

47

HOW TO KNOW THE FRESH-WATER ALGAE

66a Cells with distinct sheaths; cells inclosed in layered colonial mu-
cilage. See Fig. 41 GLOEOCYST1S

66b Cells without distinct sheaths; colonial mucilage not layered. .67

Figure 54

67a Chloroplast cup-shaped with a conspicuous pyrenoid (a doughnut-
shaped, starch-storing body, usually shiny); colony often includ-
ing clusters of smaller daughter cells. Fig. 54. . SPHAEROCYSTIS

Fig. 54. Sphaerocystis Schroeteri Chod.

This plant, of which there is only 1
species in North American records,
should be compared with Planktosphae-
ria (Fig. 55). There is 1, cup-shaped
choroplast, and the colony almost in-
variably shows clusters of small cells
formed by the division of the parent
cell into 4 or 8 daughter-cells. There
is a gelatinous sheath but the individual cells do not show the lamel-
lated envelope of Gloeocystis, a genus which may be confused with
Sphaerocystis. Young cells of Planktosphaeria may have a cup-shaped
chloroplast.

67b Chloroplasts several polygonal plates, each with a pyrenoid (chlo-
roplast single when cells are young); colony not containing clusters
of daughter-cells. Fig. 55 PLANKTOSPHAERIA

Fig. 55. Planktosphaeria gelatinosa G. M. Smith.

This plant, only one species known, occurs most-
ly in the tychoplankton (shallow water plankton
among other algae) but may appear also in the
open water plankton (euplankton). Unless care is
used it is easy to confuse this plant with Gloeo-
cystis (Fig. 41) or Sphaerocystis (Fig. 54), or other
small, green spherical cells. When mature the
cells are recognizable by their angular, 5-sided
chloroplasts, each of which contains a pyrenoid.
The colonial sheath is often very thin and diffi-
cult of determination.

Figure 55

68a (65) Cells lunate or sickle-shaped, tapering and pointed at the
apices 69

68b Cells bean-shaped, oval or spindle-shaped, the apices sometimes
tapered but rounded or blunt '

48

HOW TO KNOW THE FRESH-WATER ALGAE

•y&

Figure 56

69a Cells decidedly curved with the 2 poles nearly touching one an-
other, arranged in scattered groups of 4 with convex walls apposed.
Fig. 56 KIRCHNER1ELLA

Fig. 56 a, Kirchneriella lunaiis (Kirch.)
Moebius. b, K. obesa var. major (Ber.)
G. M. Smith.

The crescent-shaped or arcuate cells
of this genus are inclosed in a (some-
times indistinct) mucilage and are usu-
ally found in the open water plankton.
There are about 5 species recognized
in the United States, showing different
degrees of curvature and variations in
stoutness. The cells are mostly so
sharply curved that their apices nearly touch, whereas in Selenastrum
(Fig. 67) the cells are symmetrically crescent-shaped. They do not
occur in gelatinous envelopes whereas Kirchneriella is characterized
by the presence of a sheath.

69b Cells symmetrically crescent-shaped, in groups of 4, 2 of which
face one another. Fig. 57 TETRALLANTOS

Fig. 57. Tetrallantos Lagerheimii Teiling.

This rare species (the only one in the
genus) is widely distributed. The charac-
teristic arrangement of the cells is deter-
mined at the time that they are formed in
groups of 4 within the mother-cell. After
the mother-cell wall breaks down to release
the daughter-cells fragments of the wall may
persist as interconnecting or radiating
threads within the colonial mucilage which
is often very thin and difficult of determin-
ation.

70a Cells fusiform or spindle-shaped 72

70b Cells ovate, bean-shaped, or oblong 71

71a Cells oval, somewhat irregularly arranged in 4's, forming a flat
plate. Fig. 58 D1SPORA

Fig. 58. ^Dispora crucigenioides Printz.

Only 1 species in the United Stales,
and apparently rare. The cells are in
rather irregular rectilinear series and usu-
ally show a quartet arrangement within
a flat gelatinous sheath. It should be
compared with Crucigenia (Fig. 72), espe-
cially C. irregularis in which the cells are
more definitely arranged in 4's.

crs>

Figure 57

§® m

@$ ®@

Figure 58

49

Figure 59

HOW TO KNOW THE FRESH-WATER ALGAE

71b Cells bean-shaped or oblong, reproducing by autospores which are
retained within the enlarged mother-cell wall (the wall may gela-
tinize and appear as a mucilaginous sheath). Fig. 59

NEPHROCYT1UM

Fig. 59 a, Nephrocytium ecdysiscepa-
num W. West; b, N. obesum W. & G.
S. West; c, N. limneticum (G. M.
Smith) G. M. Smith; d, N. lunaium W.
West.

Most of the five species of this genus

which occur in the United States have

reniform or bean-shaped cells, often with

one convex wall and one flattened or

less convex than the other. They occur

in mixtures of algae in the tychoplank-

ton but two species of the genus, N.

Agardhianum Naeg. and N. limneticum

G. M. Smith are usually found in the euplankton. The former has

elongate, almost vermiform cells which are sometimes curved or spirally

twisted.

72a Cells in linear pairs, 1 or several pairs within a common mucilagin-
ous investment (cells with long axes approximately parallel, some-
times solitary). See Fig. 38 ELAKATOTHR1X

72b Cells arranged in parallel bundles, reproducing by autospores

(daughter colonies forming within the mother-cell). Fig. 60

QUADRIGULA

Fig. 60. Quadrigula Chodati (Tan-

ner-Fullman) G. M. Smith.

There are 3 species found in
the euplankton of lakes, all of
which have elongate, fusiform or
'cigar'-shaped cells. The species
illustrated has cells with bluntly
rounded poles whereas the other
two have pointed apices. The
cells occur in rather compact bun-
dles of 4, all lying parallel in the
colonial envelope.

Figure 60

73a (38) Cells (or some of them in the colony) bearing long, gelatinous
bristles or scales, or hairs 74

73b Cells without bristles but some with spines shorter or longer than
the cell 76

50

HOW TO KNOW THE FRESH-WATER ALGAE

74a Cells arranged in a quadrate colony of 4 cells interconnected by
strands, each cell bearing a scale-like fragment of mother-cell wall.
See Fig. 43 CORONASTRUM

74b Colony formed otherwise 75

75a Cells forming an attached, compact cluster within the mother-cell
wall which bears a branched hair that has no sheath. Fig. 61.

DICRANOCHAETE

Fig. 61. Dicranochaete renitormis Heiron.

Although this curious plant usually occurs
as single cells, the individuals may be clus-
tered as a result of recent cell division. It
grows on filamentous algae and other sub-
merged aquatic plants and apparently is very
rare. The unique branched seta which is pro-
duced from the lower side of the cell makes
identifications certain.

Figure 61

75b Cells loosely arranged side by side in a cluster, each bearing an

unbranched hair with a basal sheath. Fig. 62

CHAETOSPHAERID1UM

Fig. 62. Chaetosphaeridium globosum
(Nordst.) Klebahn. a, group of cells;
b, one cell showing tube-like utricle
which may extend from one cell to an-
other and so form a sort of colony.

This globular, hair-bearing cell occurs
eithor singly or in aggregations of 2 to 8
individuals on larger algae, on Utriculaiia
or on other aquatic plants. This genus
and Dicranochaete (Fig. 61) are anomal-
ous members of a family of filamentous algae. Their inclusion in the
Coleochaetaceae is based upon the type of seta (a bristle with a
sheathed base) which they have in common.

Figure 62

76a (73) Cells attached at the ends of branching gelatinous stalks,

77
epizoic on microcrustaceans

76b Cells not at the ends of branching gelatinous strands; not epizoic . 78

51

HOW TO KNOW THE FRESH-WATER ALGAE

77a Cells ellipsoid or somewhat fusiform; chloroplast 1 or 2 longitudinal
lateral bands. Fig. 63 CHLORANGIUM

Figure 63

Fig. 63. Chlorangium stentorinum (Ehr.) Stein.

This organism becomes attached, anterior end
down, to small crustaceans and other microscopic
animals by means ot a gelatinous stalk. Although
a swimming cell, the tlagella are thrown off and the
organism continues to divide, the stalk becoming
branched as new individuals arise so that a colony
results. Some small animals such as Cyclops may
go swimming about with veritable plumes of the
green cells growing on their antennae. The cells
have 2 elongate, parietal chloroplasts. Compare
Chlorangium with Colacium (Fig. 64).

77b Cells ovate to oblong or ovoid; chloroplasts numerous ovoid discs.
Fig. 64 COLACIUM

Fig. 64 a, Colacium arbuscula Stein; b,
C. vesiculosum Ehr.

Microscopic animals, especially crusta-
ceans, may appear green because of the
large numbers of Colacium individuals at-
tached to them, either singly or in plume-
like clusters. Like Chlorangium (Tig. 63)
this organism is a motile green cell which,
however, has numerous Eugiena-like chlo-
roplasts (Fig. 8) and a conspicuous red
b pigment-spot. The rather specific associ-
ation of the algal cells with the animal
host incites speculation as to how this
relationship is maintained.

Figure 64

78a (76) Cells ellipsoid or spindle-shaped, attached end to end form-
ing loose branching chains. Fig. 65 DACTYLOCOCCUS

Sfc*5^

Fig. 65. Dactylococcus intusionum Naeg. (Re-
drawn from Smith.)

This anomalous genus is known from soil
collections of aigae. The characteristic chain-
like arrangement of the cells develops as the
cells are cultivated whereas they probably
are solitary in nature.

Figure 65

78b Cells not arranged in branching chains

79

52

HOW TO KNOW THE FRESH-WATER ALGAE

79a Cells globose or flatttened on some sides from mutual compres-
sion; forming green films on moist substrates. Fig. 66

PHOTOCOCCUS

Fig. 66. Protococcus viridis Ag. a, clump of
cells; b, filamentous tendency in cell ar-
rangement.

This plant, also known the world over as
Pleurococcus vulgaris Menegh., forms the fa-
miliar green film on the moist side of trees,
rocks, wet boards, etc. Essentially unicellular,
it forms clumps from repeated cell division
and the occasional tendency to form filaments
has led students of the algae to classify it in
the filamentous order, Ulotrichales, and to con-
sider it as having been reduced to its present
simple morphological condition. It reproduces
only by cell division and is easily distributed by wind, water, and
insects so that it appears throughout the world almost everywhere
that subaerial life can exist.

Figure 66

79b Cells differently shaped, not producing films on aerial substrates 80

80a Cells crescent-shaped or sharply acicular (needle-shaped)

81

80b Cells some other shape

82

81a Cells strongly crescent-shaped, closely clustered but not entangled.
Fig. 67 SELENASTRUM

Fig. 67. Selenastrum gracile Reinsch.

These gracefully curved cells occur
in clusters of from 4 to 32, with a ten-
dency to have the convex or 'outer'
walls approximated. The curvature of
the 'outer' and 'inner' walls of the
crescent are more nearly the same
than in the somewhat similarly shaped
Figure 67 cells of Kirchneriella (Fig. 56), a genus

which has cells irregularly arranged within a gelatinous envelope.
Four species are commonly found in this country, mostly differentiated
by size and degree of curvature. Mixtures of algae from shallow water
situations often include Selenastrum but they may be found also in
the euplankton.

53

HOW TO KNOW THE FRESH-WATER ALGAE

81b Cells straight or only slightly crescent-shaped, loosely entangled
about one another (frequently solitary rather than colonial). Fig.
68 ANKISTRODESMUS

Fig. 68a. Ankistrodesmus falcatus (Cor-
da) Ralfs; b. A. convolutus Corda; c,
A. Braunii (Naeg.) Brunn.; d, A. fractus
(W. & G. S. West) Brunn.

Although there are 5 or 6 species of
this genus common in the United States,
A. falcatus (Corda) Ralfs is probably the
one most frequently collected. It occurs
as solitary or loosely clustered needles
Figure 68 or slightly fusiform-shaped cells inter-

mingled with other algae, or sometimes

forming almost pure growths in artificial pools or in laboratory aquaria.

One species, A. spiralis (Turn.) Lemm., has needle-shaped cells spirally

twisted about one another to form bundles.

82a (80) Cells attached either along their side or end walls to form
definite patterns, nets, plates, triangular clusters, or short rows. .83
end only in juxtaposition. See Fig. 57 TETRALLANTOS

82b Cells attached otherwise, if adjoined by lateral walls then not
forming definite patterns 98

83a Cells cylindrical, one cell attached by 2 others at the end walls
repeatedly to form a network. Fig. 69 HYDRODICTYON

Fig. 69. Hydrodictyon reticulatum (L.) Lager-
heim.

This is the familiar "water-net" which often
grows in such dense mats in lakes, small
ponds and irrigation ditches as to become a
troublesome weed. This unique alga is able
to reproduce very rapidly because each cell
of the net in turn produces a new cylindrical
net of small cells within it, which upon es-
cape enlarge enormously, each cell again
producing a net. The nets are of macroscop-
ic size and there is a report of one being
found more than 2 feet in length. It is thought that the first written
records referring to a specific alga is of Hydrodictyon in ancient
Chinese literature.

83b Cells some other shape, not attached to form a network

84

84a Cells arranged to form flat, circular or rectangular plates. (Fig. 70)
85

54

HOW TO KNOW THE FRESH-WATER ALGAE

84b Cells not arranged to form flat plates

88

85a Cells forming circular plates (sometimes irregularly subcircular),
the marginal cells sometimes different in shape from those within.
Fig. 70 PEDIASTRUM

Figure 70

Fig. 70 a, Pediastrum simplex (Mey-
en) Lemm.; b, P. tetras (Ehr.) Ralfs;
c # P. hirodiotum var. emarginatum
fa. convexum Pres.; d. P. Boryanum
(Turp.) Menegh.; e, P. obfusum
Lucks.

Although there are many species of this
genus all may be identified by the plate-
\ like arrangement of cells. The plate may
be continuous with internal cells different in
shape from those at the periphery, or there
may be interstices with all cells in the colony
about the same shape. One, P. tetras (Ehr.)
Ralfs, forms plates of but 4 cells. Rarely
a 2-celled colony may appear, in which case
it might be mistaken for Euastropsis (Fig. 33).

85b Cells not arranged to form circular plates 86

86a Cells triangular or ovoid, forming guadrangular plates, bearing
one or more spines. Fig. 71 TETRASTRUM

Fig. 71.
Chod.

Tetrostrum heterocanthum (Nordst.)

There are probably only three species of this
genus repotted from the United States. They
occur in the euplankton and are readily identi-
fied by their arrangement in flat plates of four,
the cells bearing 1 to 4 spines on the outer free
walls.

Figure 71

86b Cells rectangular or trapezoidal or if oval, without spines

87

55

HOW TO KNOW THE FRESH-WATER ALGAE

87a Cells rectangular, oval, or trapezoidal, the outer walls entire (not
incised); arranged to form quadrate plates in 4's or in multiples
of 4. Fig. 72 CRUC1GENIA

Fig. 72 a, Crucigenia tetrapedia (Kirch.)
W. & G. S. West; b, C. rectangularis
(A. Braun) Gay.

These cells (like Tetrastrum, Fig. 71)
occur in 4's but usually form multiple
colonies of rectangular plates. There
are about a dozen species in the United
States, differentiated by the shape of
the cell which may be oval, triangular
or elliptic in outline.

Figure 72

87b Cells trapezoidal, the outer free walls deeply incised, forming oval
or somewhat angular plates (only 4 cells present in some colonies).
See Fig. 70 PEDIASTRUM

88a (84) Cell walls with spines 89

88b Cell walls without spines

92

89a Cells ellipsoid, spines numerous, needle-like; cells (usually solitary)
arranged side by side because of interlocking spines, indefinite in
number. Fig. 73 FRANCEIA

Fig. 73. Fianceia Droescheri (Lemm.) G. M. Smith.

This and two other species occur in the euplank-
ton of lakes but rather rarely. The cells are solitary
but they may be clustered from the interlocking of
the needle-like spines which cover the wall. Lager-
heimia (Fig. 118) has a similar shape and needle-
like spines that are confined to the poles or to the
mid-region of the cell.

Figure 73

89b Cells ovoid or spherical; spines few (1-4), cells definitely arranged
and definite in number 90

56

HOW TO KNOW THE FRESH-WATER ALGAE

90a Cells ovoid, arranged side by side in one or two alternating rows;
spines short, mostly arising from the poles of the cells only. Fig. 74.
SCENEDESMUS

Fig. 74. a, Scenedesmus quadricauda (Turp.)
de Breb.; b, S. bijuga var. alternans
(Reinsch) Hansg.; c. S. incrassatulus var.
mononae G. M. Smith (Redrawn from Tif-
fany); d, S. opoliensis P. Richter.
There are numerous species of this genus
occurring both in the euplankton and the
tychoplankton (intermingled, free-floating al-
gae in shallow water near shore). The cells
Figure 74 are oval, fusiform, or crescent-shaped ac-

cording to species, and occur side by side in one series oi 4, or in a
double, alternating series of 8; rarely a single series of cells will have
8 or 12 cells. Certain species of Scenedesmus invariably appear in
laboratory cultures, often coloring the water green. Under unnatural
conditions the cells often appear singly rather than in colonies of 4.
Perhaps the most common species is S. quadricauda (Turp.) de Breb in
which the two outer cells of the series bear a long curved spine at
their poles.

90b Cells spherical, in groups of 4 or in multiples of 4 to form com-
pound colonies, outer walls bearing long, slender spines 91

91a Colony triangular, spines 1-7. Fig. 75 MICRACT1N1UM

Fig. 75. Micractinium pusillum Fres.

This rare alga occurs in the euplankton,
having clusters of 4 round cells arranged
in the form of a pyramid. Each cell bears
1 to several long, tapering spines. An-
other species which is also seldom seen is
M. guadrisefum (Lemm.) G. M. Smith, hav-
ing oval or elliptic cells.

Figure 75

91b Colony pyramidal but with outer wall bearing a single stout spine.
Fig. 76 ERRERELLA

Fig. 76. Eneiella bornhemiensis Conrad.

Cells of this plant, of which there is but a
single species, are arranged to form a 3-dimen-
sion pyramid. It is 'known only from the eu-
plankton and apparently is very rare.

Figure 76

57

HOW TO KNOW THE FRESH-WATER ALGAE

92a (88) Cells spherical or polygonal, arranged to form hollow, spheri-
cal or many-sided colonies; cells adjoined by interconnecting pro-
tuberances of the mucilaginous sheath. Fig. 77. . . .COELASTRUM

Fig. 77 a, Coelastium cambiicum
Archer (Redrawn from Smith); b,
C. microporum Naegeli.

As the name suggests, cells of
this plant are arranged to form a
hollow colony. Six or seven spe-
cies are known from this country,
differing in the shape of the cell
and in the length of the intercon-
necting processes. Common in both euplankton and in the tycho-
plankton.

Figure 77

92b Cells not forming hollow colonies and not so adjoined

93

93a Cells fusiform, radiating from a common center. Fig. 78

ACT1NASTRUM

Fig. 78. Actinastrum Hantzschii Lag.

These "cigar"-shaped cells are arranged
in radiating colonies. This species is more
common in the plankton than is A. gracil-
limum G. M. Smith which has pointed
rather than truncate apices.

Figure 78
93b Cells shaped otherwise, not forming a colony of radiating cells . . 94

94a Cells ellipsoid to fusiform, adjoined end to end. forming chain-like
series. See Fig. 65 DACTYLOCOCCUS

94b Cells not forming chains 95

95a Cells ovoid, ellipsoid or fusiform, adjoined by their lateral wall to
form a row of 4 in a single series, or a double series in which the
cells are alternating. See Fig. 74 SCENEDESMUS

58

HOW TO KNOW THE FRESH-WATER ALGAE

95b Cells globular or variously shaped, not attached side by side in
one plane 96

96a Cells fusiform or trapezoidal, attached with their long axes paral-
lel about a common center. Fig. 79 TETRADESMUS

Figure 79

Fig. 79. Tetradesmus Smithii Presc.

This plant resembles some Scenedesmus spe-
cies (Fig. 74) but differs in having the cells qua-
drately arranged rather than in a series in one
plane. There are but two species known in this
country, both of them from the euplcmkton of
Wisconsin lakes. T. wisconsinense G. M. Smith
has trapezoidal cells.

96b Cells some other shape and not attached about a common center . 97

97a Cells crescent-shaped, in groups of 4, 2 with concave sides toward
one another, the other 2 cells in another plane with poles at one
end only in juxtaposition. See Fig. 57 TETRALLANTOS

97b Cells sickle-shaped, fusiform or crescent-shaped, twisted about one
another. See Fig. 68 ANKISTRODESMUS

98a (82) Cells adjoined by gelatinous strands or threads formed from
the remains of old mother-cell walls 99

98b Cells not adjoined by remains of old mother-cell walls 101

99a Cells spindle-shaped, in clusters of 4-8-16 at the ends of radiating
gelatinous stalks. Fig. 80 ? ACTIDESMIUM

Fig. 80. Actidesmium Hookeri Reinsch.

This rare plant occurs in the tychoplankton
of shallow pools. The star-shaped clusters of
cells at the ends of radiating (sometimes dicho-
tomously branched) gelatinous stalks render it
easy of identification.

59

Figure 80

HOW TO KNOW THE FRESH-WATER ALGAE
99b Cells shaped or arranged otherwise

100

100a Cells globose, in clumps of 4-8, the groups held together by loop-
like fragments of old mother-cell wall. Fig. 81 WESTELLA

Fig. 81. Westella botryoides
de Wild.

(W. West)

Figure 81

This plant should be compared with
Dictyosphaerium (Fig. 53) which it may
resemble superficially at times. Westella
has no gelatinous envelope and although
there are strands left by the old mother-
cell wall they do not produce the regular
radiate structures as in Dictyosphaerium.

100b Cells appearing oval and bean-shaped in the same colony, in
clusters at the ends of radiating, branched strands. See Fig. 52.

D1MOHPHOCOCCUS

101a (98) Cells pear-shaped, bean-shaped, or somewhat crescent-
shaped, the outer free wall bearing 2 to 4 stout spines; cells ar-
ranged at the ends of radiating, stout, gelatinous strands to form
a globular colony. Fig. 82 SORASTRUM

Fig. 82. Sorasfrum americanum (Bohlin) Schmidle.

There are only 2 species of this genus report-
ed from the United States, of which S. spinulosum
Naeg. is probably the more common in the
plankton. This species has relatively stout
short spines and the basal pedicel is scarcely
developed so that the colony appears as a
compact cluster.

Figure 82

101b Cells not so arranged, without spines or with spines different
than above 102

60

HOW TO KNOW THE FRESH-WATER ALGAE

102a Cells spherical or oval, in 2's and 4's. separated from one an-
other by semi-opaque masses of dark mucilage which iorm
X-shaped bands. Fig. 83 GLOEOTAENIUM

Fig. 83. Gloeotaenium Loitelsberqerianum
Hansg.

This unique plant is rare but widely dis-
tributed. When it occurs at all it is rela-
tively abundant. Collections from the mix-
ture of algae in shallow water ponds and
bogs often yield this species.

Figure 83

102b Cells not separated from one another by masses of dark
mucilage 103

103a Cells bearing long, needle-like spines (colonial only because of
entangled spines). Fig. 84 GOLENKINIA

Fig. 84. Golenkinio radiata (Chodat) Wille.

There are but 2 species of this genus re-
ported, both of them common in two sam-
ples from the open water of lakes. G.
radiata Chod. has spines 2 to 3 times the
diameter of the cell in length, whereas G.
paucispina West & West has more numer-
ous spines that are about equal to the cell
diameter in length.

Figure 84

103b Cells without spines 104

104a Cells inclosed by old mother-cell wall

105

104b Cells not inclosed by old mother-cell wall

106

105a Cells somewhat bean-shaped or kidney-shaped, or broadly ellip-
tic (old mother-cell wall often appearing as a mucilaginous sheath).
See Fig. 59 NEPHROCYTIUM

61

HOW TO KNOW THE FRESH-WATER ALGAE

105b Cells elliptic, lemon-shaped, or nearly cylindrical, 1 to several
generations of mother-cell walls inclosing daughter cells. Fig. 85.

OOCYSTIS

Fig. 85. a, Oocystis Eremosphaeiia
G. M. Smith; b, O. Borgei Snow.

There are several species of this
genus common in both the euplank-
ton and the tychoplankton. The vari-
ous forms are differentiated by the
presence or absence of nodules at
the poles and by the number of
chloroplasts. Two or 3 generations
of cell walls may be inclosed within an original mother-cell wall which
enlarges so that it often appears as a gelatinous sheath and is, there-
fore, misleading as a differentiating genus character.

106a Cells spherical, occurring as evenly distributed clumps within the
gelatinous sheaths which sometimes are lacking; chloroplasts sev-
eral angular plates. See Fig. 55 PLANKTOSPHAERIA

106b Cells variously shaped but not distributed in clumps as above;
often densely aggregated; chloroplast 1, parietal 107

107a Cells spherical or angular from mutual compression when oc-
curring in clumps; subaerial 108

107b Cells fusiform or needle-shaped, aguatic. See Fig. 68

ANKISTRODESMUS

108a Cells spherical, clustered but not adjoined, sometimes solitary.
See Fig. 42 CHLOROCOCCUM

108b Cells in dense clumps, forming a film or a layer on moist sub-
aerial substrates; cells spherical or angular from mutual com-
pression. See Fig. 66 PROTOCOCCUS

(PLEUROCOCCUS)

109a (36) Cells crescent-shaped, or sickle-shaped, with sharply pointed
or narrowly rounded and tapering apices 110

109b Cells some other shape 117

62

HOW TO KNOW THE FRESH-WATER ALGAE

Figure 86

110a With 2 axial chloroplasts bearing longitudinal ridges, a chlorc-
plast in either horn of the cell; pyrenoids conspicuous, usually in
an axial row. Fig. 86 CLOSTER1UM

Fig. 86. Closterium spp. Two of the
many variations in curvature and
cell proportions exhibited in this
genus.

This desmid usually has distinct-
ly crescent-shaped cells, but some
species are nearly straight, or have
the outer margin of the cell bowed
and the inner almost straight. A few
species have the poles extended to
form long, almost straight, needle-like processes which are swollen at
the tip. Although this genus does not show the constriction of the cell
to form two semi-cells characteristic of most other true desmids, the
cell contents are symmetrically divided into 2 portions with the nucleus
centrally located. A never-failing characteristic of Closterium is the
polar vacuoles containing vibrating granules of gypsum.

110b Cells with 1 chloroplast, or with parietal chloroplasts not arranged
as above HI

Ilia Cells only slightly crescent-shaped, (usually straight or nearly so,
and often irregularly curved), with poles drawn out into fine
points 112

111b Cells definitely crescent-shaped, or with poles not drawn out into,
fine points " *"

112a Cells attached by a slender stipe to other algae or to microfauna.
Fig. 87 CHARAC1UM

Fig. 87. a, Characium D e b a r y a n u m
(Reinsch) DeToni; b, C. ornithocephalum
A. Braun; c, C. rostratum Reinhard.
There are numerous species in this
genus, differentiated by shape of cell and
by presence or absence of a stalk. Some
are very minute and are easily overlooked,
whereas others are larger and grow in as-
sociations so as to form conspicuous patch-
es on filaments of algae or on small
animals. The genus Characiopsis contains species shaped like some
of those of Characium and care should be used in determining the
color of the chloroplast and the presence or absence of a pyrenoid
in making identification. Characiopsis (Fig. 217) has a yellow pigment
predominating and starch tests are negative; is a member of the
Chrysophyta.
1 12b Cells not attached by a stipe . . ; 113

Figure 87

63

HOW TO KNOW THE FRESH-WATER ALGAE

113a Wall at the poles of the cell extended to form slender setae, one
of which may be forked; cholorplasts extending the full length of
the cell. Fig. 88 SCHROEDER1A

Fig. 88. Schroederia Judayi G. M. Smith.

One of the three species found in the
United States, S. setigera (Schrod.) Lemm.,
is the most common. The cells have
a spine at both poles which is undivided,
whereas S. ancora G. M. Smith, also fair-
ly common in plankton, has one polar
process forked at the tip. In a Michigan
pond the former species occurred as prac-
tically the only member of the plankton
throughout winter months.

Figure 88

113b Tips of the cells narrowed to fine points at least at one end with

the poles narrowly rounded, tip not seta-like but narrowly pointed;

chloroplast not extending the full length of the cell. Fig. 89 ... .

OUROCOCCUS

Fig. 89. Ourococcus bicaudatus Grob. (Redrawn
from Smith.)

This rare plant might be confused easily with
Ankistrodesmus spp. (Fig. 68) but the cells are
usually stouter. It is closely related to Elakato-
thrix (Fig. 38) in the Order Tetrasporales be-
cause the cells retain the ability to divide vege-
tatively to form new individuals, whereas in
the Order Chlorococcales, which concerns cells
similar in shape to Ourococcus, the cells cannot undergo division but
must form new individuals within the wall of the parent cell.

114a (111) Cells very slender, needle-like or sometimes fusiform (usual-
ly in clusters but sometimes solitary), often only slightly, crescent-
shaped; chloroplast parietal, the outline often discerned with dif-
ficulty. See Fig. 68 ANKISTRODESMUS

114b Cells stouter, not needle-like; definitely crescent-shaped, the chlo-
roplast parietal and definite in outline 115

64

HOW TO KNOW THE FRESH-WATER ALGAE

115a Cells bearing a stout spine at either end. Fig. 90

CLOSTER1DWM

Fig. 90. Closteiidium lunula Reinsch.

This species has two relatives which are
nearly straight. It can be differentiated from
Closterium (Fig. 86) by the fact that there is but
a single chloroplast, and by the absence of the
terminal vacuoles with vibrating granules.

Figure 90
115b Cells without stout spines at the ends 116

116a Cells inclosed in a mucilage (usually in clusters but sometimes
solitary); in some species the curvature is so great that the tips
nearly touch. See Fig. 56 K1RCHNERIELLA

116b Cells not inclosed in mucilage (rarely in mucilage; see Fig. 67):
usually in clusters but sometimes found solitary; curvature of the
inner margin nearly that of the outer; tips of cell not almost touch-
ing. See Fig. 67 SELENASTRUM

117a (109) Living in the tissues of higher plants or in animals 118

117b Not living in tissues of plants or in animals 121

118a Cells globose, numerous within protozoa, sponges. Hydra, et al.
Fig# 91 CHLORELLA

Fig. 91. a, Chlorella (Zoochloiella) para-
sitica Brandt (in Ophrydium, a co-
lonial ciliate); b, C. (Zoochlorella) con-
ductrix Brandt (in Hydra); c, C. ellip-
soidea Gerneck, two cells enlarged
to show parietal chloroplasts.

These small cells occur singly or in
gregarious masses, either free-living or
contained within the bodies of animals
such as protozoa and sponges. As en-
dozoic plants they are often known as
Zoochlorella. Species are not well-de-
fined and mostly are differentiated by size. The chloroplast is thin
and cup shaped. Like other members of the Chlorococcales, reproduc-
tion takes place by internal cell division (in this case forming non-
motile autospores). Chlorella is a genus that has been and is now
being used in culture for investigations of the" process of photosyn-
thesis and the synthesis of proteins.

Figure 91

65

HOW TO KNOW THE FRESH-WATER ALGAE

118b Cells some other shape; not living within animals 119

119a Plant a much-branched, coenocytic tube (multi-nucleate and with-
out cross walls), growing in leaves of Araceae (Indian Turnip).
Fig. 92 PHYLLOSIPHON

Fig. 92. Phyllosiphon Arisari

Kuhn. a, portion of thallus
showing tangled threads; b,
habit of thallus in tissue of
host (redrawn from Just).

This branched, tubular plant
is non-cellular; forms green
patches in the leaves of higher
plants which become discolored. It may be more widely distributed
than appears to be the case at present, but so far it is known only from
northern and eastern sections of the United States.

Figure 92

119b Plant not a branched coenocyte

120

120a An irregularly shaped, flask-like cell in the tissues of Ambrosia
(ragweed), and other plants. Fig. 93 RHODOCHYTR1UM

Fig. 93. Rhodochytrium spilanthidis Lag.

This curiously shaped, unicellular parasite oc-
curs on a greater variety of hosts than Phyllosi-
phon (Fig. 92), but seems to be most frequent in
ragweed. It is quickly identified by the red
color and the large number of strach grain that
Figure 93 are usually present.

120b An irregularly oval, thick-walled cell in the tissues of Lemna
(duckweed). Fig. 94 CHLOROCHYTRIUM

Fig. 94. Chlorochytrium Lemnae Cohn. a,
showing net-like chloroplast (redrawn
from Bristol-Roach); b, cell in host tisue.

The duckweed, Lemna trisulca, is the
most common host for this endophytic
alga. Old plants of Lemna as they be-
come colorless in age, usually reveal min-
ute green spots caused by Chlorochytrium.

There are probably three other species in
the United States, differentiated by cell size and thickness of the wall
which is usually much lamellated.

Figure 94

66

HOW TO KNOW THE FRESH-WATER ALGAE

121a (117) Cells attached, either sessile or on a stalk 122

121b Cells free-floating or forming a film on moist earth 126

122a Cells bearing a seta or hair 123

122b Cells without setae 124

123a Setae simple (unbranched). See Fig. 62 . . CHAETOSPHAERIDIUM
123b Setae branched. See Fig. 61 D1CRANOCHAETE

124a Cells on a slender stalk or with the basal portions of the cell
narrowed to form a stalk 125

124b Cells globular, attached by a broad, short stalk. Fig. 95

MALLEOCHLORIS

Fig. 95. Malleochloris sessilis Pascher (redrawn from
Pascher).

This rare plant is to be sought on filamentous algae
such as members of the Cladophoraceae. The sheath
that incloses the cell is often reddish. Reproduction
(similar to other Tetrasporales) is by swimming spores
and by isogametes.

Figure 95

125a Cells globular, with chloroplast lying along the outer free wall;

growing on Anabaena or CoeJosphaerium. Fig. 96

STYLOSPHAER1D1UM

Fig. 96. Stylosphaeridium stipitatum (Bach.) Geit. <&
Gimesi, a, habit of cells in colonial mucilage of Coelo-
sphaerium; b, single cells showing apical position of
chloroplast.

This curious epiphyte is found in abundance when

it occurs at all as minute "hat pins" in the mucilage

•?"'i?S °* co l° ma l blue-green algae such as Coelosphaerium.

Sjfc (Fig. 319.)

'Ooo^o
o O

Figure 96

67

HOW TO KNOW THE FRESH-WATER ALGAE

125b Cells elongate-ovoid, or fusiform, or if globular, with a chloro-
plast parietal along the lateral walls. See Fig. 87. CHARACIUM
(Compare with Characiopsis, Fig. 217, a genus similar in shape,
belonging to the Chrysophyta in which the chromatophores are
yellowish-green.)

126a (121) Cells elongate-fusiform, or rod-shaped, crescent-shaped,
slightly curved, or straight; several to many times longer than
their diameter 127

126b Cells oval, circular (or nearly so), pyramidal, trapezoidal, or star-
shaped, isodiametrically angular; not more than 3 times the di-
ameter in length 146

127a Cells with narrowed apices, sometimes sharply pointed. . . 1?R

127b Cells with broadly rounded or truncate apices 133

128a Chloroplasts 2, axial, one in either horn of a crescent-shaped cell
which may be only slightly curved. See Fig. 86 CLOSTERIUM

128b Chloroplasts otherwise 129

129a Cells decidedly fusiform, one or both poles extended into setae
or sharp points 130

129b Cells not broadly fusiform 132

130a Cells actually globular but inclosed in a fusiform sheath with
longitudinal ridges. Fig. 97 DESMATRACTUM

Fig. 97. Desmafracfum bipyramidatum
Chod.) Pascher.

This unique species, the only one of
^\^~ the genus in this country, is rather rare
but seems to be widely distributed in the
plankton of both streams and lakes. The
wall is very wide and transparent, form-
Figure 97 i n g a sheath-like envelope.

68

HOW TO KNOW THE FRESH-WATER ALGAE
130b Cells themselves fusiform; without such a sheath 131

131a Setae formed by a narrowing of the cell to a fine point; chloro-
plast laminate (plate-like), not extending the full length of the cell.
See Fig. 89 OUROCOCCUS

131b Setae formed by a fine spine on the wall, extending from the
narrowed tips of the cells. See Fig. 88 SCHROEDERIA

132a (129) Cells many (20 or more) times longer than wide; the chloro-
plast with a row of pyrenoids. Fig. 98 CLOSTERIOPS1S

Figure 98

Fig. 98. Closteriopsis longissima Lemm.

There is but one species reported from this country. Although it
superficially resembles a Closterium (Fig. 86) it is easily separated on
the basis of the single, plate-like chloroplast which may be notched or
crenulate along the margin. At times the cells are slightly curved but
usually are more nearly straight than any of the species of Closterium.

132b Cells less than 20 times the diameter long; slender needles or
narrowly fusiform cells with one pyrenoid sometimes evident.
See Fig. 68 ANK1STRODESMUS

133a (127) With a notch in the ends of the cell. Fig. 99

, TETMEMORUS

Fig. 99. Tetmemorus laevis (Kuetz.) Ralfs.

This is a genus belonging to the true
desmids, having a wall in 2 pieces that
adjoin in the midregion. Species that
Figure 99 are found in this country seem to be con-

fined to highly acid situations. There are several species reported,
some with cylindrical shapes and some with the ends tapering, but
always with a prominent polar notch. A placoderm desmid.

69

HOW TO KNOW THE FRESH-WATER ALGAE

133b Without a notch in the ends of the cell 134

134a Cells crescent-shaped, with an axial chloroplast bearing ridges in
each horn. See Fig. 86 CLOSTERIUM

134b Cells not crescent-shaped, or with other types of chloroplasts. . 135

135a Cells constricted in the midregion to form 2 'semicells' which are
mirror images of one another 136

135b Cells not constricted in the midregion to form 'semicells' 141

136a Cells furnished with whorls of protuberances which bear one or
two spines; poles of the cell forked. Fig. 100 TR1PLOCERAS

Figure 100

Fig. 100. Tiiploceras gracile Bailey.

There are apparently only two species of this desmid genus in the
United States, easily identified by the whorls of spine-bearing protuber-
ances along the walls. Like a number of other desmid genera this one
seems to be confined to acid water, especially in Sphagnum bogs.

136b Cells not furnished with whorls of spiny protuberances 137

137a Cells 10 or more times longer than broad, usually cylindrical or
nearly so, with margins smooth or undulate 138

137b Cells less than 10 times their diameter in length; cylindric, fusi-
form, or tumid, usually straight but sometimes slightly curved. . 139

70

Figure 101

HOW TO KNOW THE FRESH-WATER ALGAE

138a With a circle of folds or creases at the base of the 'semicell/ with

a tooth on each fold. Fig. 101 DOCIDIUM

Fig. 101. Docidium undula-
tion Bailey.

This genus is scarcely to
be separated from PJeurofae-
nium (Fig. 102). In cells that
are living the density of the
chloroplast makes obscure the characteristic creases in the wall where
the two semicells are adjoined. One needs to focus carefully to see
these folds which produce teeth-like projections at the very outer mar-
gin of the bases of the semicell, especially in individuals which have
a granule on the fold. Another species, D. Baculum Breb., less com-
mon than the species illustrated, has smooth lateral walls.

138b Without a circle of creases at the base of the 'semicell.' Fig. 102.
PLEUROTAENIUM

Fig. 102. a, Pleurotaenium trabe-
cule! (Ehr.) Naegeli; b, P. nodo-
sum Bailey.

There are more species in this
genus than in Docidium (Fig. 101)
and they are more widely dis-
tributed. Although all of them are
elongate and usually have sub-
parallel margins, there is considerable variation in details of the shape
and in decoration of the wall. In some species the margins are nodose
or undulate; some spiny. Usually there is a circle of granules around
the poles of the cell. Some species are not so restricted in their distri-
bution as most desmids, and may occur in basic or slightly alkaline
waters as well as in acid or soft water habitats.

139a Cells with 2 star-shaped chloroplasts, one in each 'semicell.' Fig.
103 CYLINDROCYSTIS

Fig. 103. Cylindrocystis Brebissonii Menegh.

Although some of the half-dozen species of
this genus have slightly constricted cells, they
have a wall composed of one piece and have
no wall pores, which thus identifies them as
saccoderm (not true) desmids. There is one
star-shaped chloroplast with a large pyrenoid
in each half of the cell. This genus is not at
all confined to acid habitats; may occur in alkaline bogs or among
mosses, or may form gelatinous masses on wet stones in alpine
situations.

139b Cell with other types of chloroplasts 140

Figure 102

Figure 103

71

HOW TO KNOW THE FRESH-WATER ALGAE

M M -

-UU-

Figure 104

140a Cells short-cylindric, or subcylindrical; chloroplasts 1 in each 'sem-
cell' (rarely 3 or 4 chloroplasts forming transverse zones in the
cell); no vacuoles with moving granules in the poles of the cell.
Fig. 104 PENIUM

Fig. 104. Penium margaritaceum (Ehr.)
Breb.

Some species of this genus are shaped
like those of Cylindrocystis (Fig. 103)
but have a wall of two pieces that ad-
join in the midregion, and the wall usu-
ally shows punctations or granulations.
In general, Penium cells are more cylin-
drical than Cylindrocystis and because

new wall sections are built in when the cells divide, they may become

as long as some small Pleurotaenium (Fig. 102).

140b Cells slightly attenuated at the apices; chloroplasts with several
pyrenoids; vacuoles with moving granules in the poles of the cell.
See Fig. 86 CLOSTERIUM

141a (135) Chloroplasts spiral ribbons 142

141b Chloroplasts some other shape 143

142a Cells "cigar"-shaped, poles rounded. Fig. 105 SP1ROTAEN1A

Figure 105

Fig. 105. Spirotaenia condensata Breb.

This "cigar"-shaped cell is usually straight but may be slightly
curved. Although one species in the United States has an axial chloro-
plast, the others have a characteristic spirally twisted one in each cell.
The cell is never constricted in the midregion and the wall is composed
of 1 piece as in other saccoderm desmids.

142b Cells cylindrical with truncate ends. Fig. 106 GENICULARIA

Fig. 106. Genicularia e 1 e g a n s
West, a, Single cell; b, fila-
mentous arrangement.
The cells may be solitary or
occur in filaments. Although the
chloroplasts are spirally twisted
and show a superficial resemblance to Spirogya (Fig. 147) this genus
is usually identifiable by the cells being slightly enlarged at the poles.
Genicularia is classified in the Gonatozygonaceae but is closely related
to the desmids and is found associated with them in nature.

b C

Figure 106

72

HOW TO KNOW THE FRESH-WATER ALGAE

143a (141) Cells cylindrical, 10 or more times the diameter in length,
the poles truncate; wall spiny. Fig. 107 GONATOZYGON

Fig. 10 7. Gonatozygon
.. i l acuieafum Hastings.
ftUJ^ This desmid-like genus

" ViiWvW H V^ haS solitar Y cells whic ; h

' are nearly always a little

Figure 107 crooked; have walls bear-

ing long or short spines;
are not constricted at the midregion. Although usually free-floating
and intermingled with desmids, the cells may be adherent to sub-
merged plants. There is a ribbon-like chloroplast that is axial rather
than parietal. As mentioned above, Gonatozygon may be classified
with Genicularia to form the Gonatozygonaceae by some authorities,
whereas others place it with the saccoderm desmids in the family
Mesotaeniaceae.
143b Cells fusiform short-cylindric, less than 10 times the diameter

in length; wall smooth 144

144a Cells broadly fusiform or subcylindrical; 2 chloroplasts, one in
each end of the cell, bearing longitudinal ridges, usually with
notched margins. Fig. 108 NETRIUM

fe«eW&?^

mL

Figure 108

Fig. 108. Netrium digitus (Ehr.) Its. & Rothe.

These are "watermelon"- or "cucumber"-shaped cells which are sac-
coderm desmids with scarcely any or no constriction in the midregion.
Like other members of the family the cell contents are conspicuously
symmetrically divided into two portions, there being 1 (rarely more)
longitudinally ridged chloroplasts in each half of the cell. There are
5 or 6 species in this country, differentiated by shape and proportions
of the cell.

144b Cells cylindrical or narrowly fusiform, with 1 chloroplast in the
cell 145

145a Cells "cigar"-shaped; chloroplast axial with 4-6 pyrenoids. Fig.

109 ROY A

Fig. 109. floya obtusa (Breb.)

r"- 1 '-!--?.-.-:.- " — |

ft & . % q- . ;*p^

m

West & West.
This rather rare saccoderm
desmid has slightly curved
Figure 109 cylindrical cells in which

there is but a single chloro-
plast that is notched in the midregion where the nucleus is located.

73

HOW TO KNOW THE FRESH- WATER ALGAE

145b Cells elongate-ellipsoid or ovoid to subcylindrical; 1 parietal chlo-
roplast; cell contents violet-colored. See Fig. 46 . . MESOTAENIUM

146a (126) Cells constricted in the midregion 147

146b Cells not constricted in the midregion 154

147a Cells flat, nearly circular in proportions, star-like in front view,
the median incision very deep; semicells deeply lobed or in-
cised, in some species forming secondary lobes and lobules.
Fig. 110 MICRASTEMAS

Fig. 110. a, Micrasteiias americana var.;
Boldtii Gutw.; b, M. radiata Hass. var.;
c, M. ioliacea Bailey.

These are true desmids and include some
of the most beautiful microscopic objects.
Although the outline of the cell varies
greatly among the twenty or more species
in this country, they can be identified by
the flat, disc-like shape. One species, M.
ioliacea Bailey, has hooks on the polar
lobes which enmesh with those of adjoin-
ing, newly-formed cells so that false "fila-
ments" are produced.

Figure 1 10
147b Cells not flat and disc-like

148

74

^\

ffpi\

■&

^\

M

: :' : -'<j]

-

*^>J

^

JJ

\.

J

Figure 1 1 1

HOW TO KNOW THE FRESH-WATER ALGAE

148a Cells with a shallow and broad, or a deep and narrow notch in
the apex of the semicell. Fig. Ill EUASTRUM

Fig. 111. a, Euastrum pinnotum Ralfs; b,
E. pectinatum var. inevolutum West &
West.

There are numerous species in this
ydesmid genus, varying greatly in size
and shape of cell. Most of them, how-
ever, have a polar notch in the semi-
cells and, characteristic of the genus,
have more or less prominent protru-
sions and swellings on the face of the
semicell. In filled cells the latter are
difficult of determination, especially in the smaller species. The speci-
mens need to be rolled so that they can be seen from the side or top
when making microscopic examinations. Nearly all of the species of
Euastrum are limited to an acid habitat.

148b Cells without a notch in the apex of the semicell 149

149a Apex of the cell extended into 2 or more arms or lobes, the arms
usually extending radiately so that the cells are star-shaped or

triangular when seen from the top (end view). Fig. 112

STAURASTRUM

Fig. 112. a, Staurastrum rotula
Nordst., 'front' or side view; b,
end view; c, St. cornutum Arch.;
d, end view.

This is a large desmid genus
with several hundred species
which vary in shape of semicell
and type of decoration on the
wall. The chief distinguishing
characteristic is the extension of
lobes or arms in at least 3 planes
so that the cell appears radiate
when seen from the top. Many species appear like Cosmarium (Fig.
113) when seen in front view and one needs to change the plane of
focus in order to see the semicell extending up toward the observer,
or down as the case may be. A few species have arms in 1 plane
only and these are retained in the genus by virtue of the fact that the
shape and decorations of the arms (spines, verrucae, etc.) are those of
Staurastrum. Some species are definitely euplanktonic and have long
arms which give them buoyancy, whereas others are tychoplanktonic
and are intermingled with other desmids in acid swamps.
149b Apex of semicell not extended into arms, or if with arms these
not radiating in 3 planes 150

Figure 1 1 2

75

HOW TO KNOW THE FRESH-WATER ALGAE

150a Semicells with 2 extended arms at their apices as seen in front
view, narrowly elliptic when seen from the top. See Fig. 112 14.
STAURASTRUM

Fig. 112V2. Staurastrum leptocladum Nordst.

150b Semicells compressed or rounded when seen from the top or side,
not with radiating arms 151

151a Margin of cell furnished with spines 152

151b Margin of cell without spines, although sometimes granular. Fig.
113 COSMARIUM

Fig. 113. a-c. Comarium panamense Presc;
b, side view; c, top view; d, C. margarita-
tum (Lund.) Roy & Biss., front and side view.

Like the genus Staurastrum (Fig. 112) Cos-
marium includes several hundred species with
considerable variation in shape of semicell
and manner of wall decoration (granules,
teeth, scrobiculations). Nearly all are com-
pressed or rounded when seen from the side
or top, regardless of their shape when seen
from the front or broad side.

Figure 1 1 3

152a Face of semicell with protuberances or with the wall thickened
in the midregion (best seen when the cell is rolled to a lateral
view position) 153

152b Face of semicell without swellings or protuberances. Fig. 114.
ARTHRODESMUS

Fig. 114. Arthrodesmus incus (Breb.) Hass.

This genus has compressed cells like
Cosmarium but the angles bear relatively
stout spines. The wall is smooth in this
genus, there being no granules, pits or
swellings.

Figure 1 14

76

HOW TO KNOW THE FRESH-WATER ALGAE

153a Apex of semicell furnished with prominent spines; facial protuber-
ance (if any) one large low swelling, the wall thickened here and
often pitted or punctate. Fig. 115 XANTHIDWM

Fig. 115. Xanthidium cristotum var. un-
cinatum Hass.

This genus too, like Arthrodesmus
(Fig. 114) has cells that are compressed
so that they are narrow when seen from
the side or top. There is usually a
facial swelling in the center of the semi-
cell and all angles bear stout spines or
short arms that are tipped with spines.

Figure 115 Some forms have granules on the wall.

There is less variation in the shape of the semicell in this genus than
in some of the other desmids.

153b Apex without spines or with a short, tooth-like spine at either
side. See Fig. Ill EUASTRUM

154a (146) Cells spherical, inclosed by a spindle-shaped envelop which
has longitudinal ridges. See Fig. 97 DESMATRACTUM

154b Cells not inclosed in such an envelope 155

155a Cells oval, ovoid, spherical or ellipsoid 156

155b Cells angular, pyramidal, trapeziform, or polygonal 183

77

HOW TO KNOW THE FRESH-WATER ALGAE

156a Cells subcylindrical or ovoid, small, less than 4.5 ^ in diameter,
with a parietal plate-like chloroplast at one or both ends. Fig.
116 NANNOCHLOR1S

Fig. 116. Nannochloris bacillaris Naum.

These tiny cells are solitary and are
without a gelantinous sheath. They are
able to undergo cell division in vegeta-
tive reproduction and hence are assign-
able to the Coccomyxaceae along with
Elakatothrix (Fig. 38) and Dactylothece (Fig.
Figure 116 ^7). It is a frequenter of laboratory cul-

ture.

156b Cells different in size and shape, or with a different type of
chloroplast 157

157a Cells bearing spines or decorated with ridges 158

157b Cells without spines or decorations 164

158a Spine length greater than the diameter of the cell 159

158b Spine length less than the diameter of the cell; wall usually
decorated with a network of thickenings 163

159a Spines not tapering from base to apex, long and slender 161

159b Spines tapering to apex, long and slender, or short and stout. . 160

160a Spines stout, broad at the base and tapering. Fig. 117

ECHINOSPHAERELLA

Fig. 117. Echinosphaerella limnetica G. M. Smith.

This is a relatively rare species from the
euplankton. In making identification care should
be used in distinguishing the single parietal
chloroplast by which the plant may be differ-
entiated from some of the spiny zygospores of
desmids (in which the cell content appears
dark and massive, with no definitely shaped
Figure 117 chloroplast distinguishable).

78

HOW TO KNOW THE FRESH-WATER ALGAE

160b Spines long and slender, gradually tapering in the basal part for
a short distance, and then abruptly narrowed to a needle. Fig.

117

ACANTHOSPHAERA

Fig. 117 ^2 . Acanthosphaera Zachariasi Lemm.

This plant can be distinguished from Echi-
nosphaerella (Fig. 117) because the spines are
long and somewhat needle-like, arising from
a base which is decidedly thicker than in
the outer section.

Figure 117%

161a (159) Cells round. See Fig. 84 GOLENKINIA

161b Cells oval or ellipsoid 162

162a Spines at the poles or at the equator of the cell. Fig. 118

LAGERHEIM1A (CHODATELLA)

Fig. 118. a, Lctgerheimia longiseta (Lemm.)
Printz; b, L. quadriseta (Lemm.) G. M.
Smith.

Unlike Franceia (Fig. 73) cells of this
genus have long, needle-like spines con-
fined to the poles or to the poles and the
equator. There are 3 or 4 species reported
from this country which are differentiated
on the basis of cell shape and arrange-
ment of spines. All are fairly common
Figure 118 in the euplankton.

162b Spines distributed over the cell wall. See Fig. 73 FRANCEIA

79

HOW TO KNOW THE FRESH-WATER ALGAE

163a (158) Cells round. Fig. 119 TROCH1SC1A

Fig. 119. a, Trochiscia gronulata (Reinsch)
Hansg.; b, T. obtusa (Reinsch) Hansg.;
c, T. reticularis (Reinsch) Hansg.
There are 5 or 6 species of this genus,
all solitary cells, which may be differ-
entiated by the type of wall decoration.
It is a little-understood genus and some
of the described species are doubtless the
zygospores of other algae. Some may be
the encysted or resting stages of still
other forms. In making identification of
plants with the outward characteristics of Trochiscia care should be
used in identifying the several disc-like chloroplasts which this genus
possesses.

163b Cells oval. Fig. 120 BOHLINIA

Fig. 120. Bohlinia echidna (Bohlin)
Lemm.

This rather unique species (the
only one in the genus) appears in
i amorphous gelatinous masses. Re-
production is by internal cell divi-
sion to form autospores. Although
older cells are characteristically
spiny recently formed individuals
may be smooth-walled. The ob-
server should examine the plant mass for remains of the old cell walls
which will show evidence of the spinescence.

Figure 120

164a (157) Cells associated with fungi to form thalli of lichens. Fig.
121 TREBOUXIA

Fig. 121. Trebouxia Cladoniae (Chod.) G. M. Smith.

This species is an inhabitor of lichens and appar-
ently occurs nowhere else. The cells are spherical
and contain an axial rather than a parietal chloro-
plast like most of the other members of the Chlorococ-
cales.

Figure 121

164b Cells not associated with fungi in lichens 165

165a Chloroplast 1, central, with radiating lobes extending to the wall

166

80

HOW TO KNOW THE FRESH-WATER ALGAE

165b Chloroplast not axial, or more than 1 in a cell, without radiating
arms 167

166a Chloroplast definitely star-shaped with a central pyrenoid; cells
spherical. See Fig. 51 ASTEROCOCCUS

166b Chloroplast irregularly lobed, not symmetrically radiate, without
a pyrenoid; cells pyriform. Fig. 122 MYRMEC1A

s- — -v Fig. 122. Myimecia aquatica G. M. Smith (re-

J/^H^i^x >Q\ drawn from Smith).

W r $^M%&) v^&'i These cells are either spherical or somewhat

xsi ''-^W \£±j/ pear-shaped and usually show a thickening of

the wall at one side, giving them an unsymmetri-
Figure 122 cal shape. Although the genus was originally

described from aerial situations, specimens in
this country have been collected from aquatic habitats.

167a (165) Cells spherical 168

167b Cells oval or ellipsoid 174

168a Cells large, wall thin; chloroplast irregular in shape and lumpy
with starch grains, arranged in radiating strands from the center
of the cell, and also parietal. Fig. 123 EREMOSPHAERA

Fig. 123. Eremosphaera viridis De Bary.

/Z&& w-.. "IT^v This is one of the largest spherical cells

//r® '. <S\ (up to 800 microns in diameter) encountered

II& ■» S-- - o°%. A\ amon< ? tne unicellular algae. Although usu-

m 3^^|||p Q Jl a ^Y solitary it may appear in clusters within

Q£»0 v^^fep^ °<d3/ t ^ ie °ld mother-cell wall. There is one other

\\G £$■ W^k^ Jal rare species (with oblate-spheroidal cells) but

X§><£>&& ''** *W/ the plant illustrated is fairly common in habi-

^^T_ < ^°/y ta * s wnere desmids abound. The numerous

^=^~2^^^^ disc-like chloroplasts are often lumpy and

irregular in shape because of the starch
grains which collect about them.

168b Cells not as above

169

81

HOW TO KNOW THE FRESH-WATER ALGAE

169a Cells enclosed by a mucilaginous sheath 170

169b Cells not enclosed by a sheath 171

170a Cells eccentrically placed in a sheath which has numerous lamel-
lations (layers); pyrenoid lacking. Fig. 124 UROCOCCUS

Fig. 124. Urococcus insignis (Hass.) Kuetz.

-•'•■.:

Although holding a place in the Tetra-
sporales according to its assignment in the
past, this reddish-colored cell has been
shown to be an encysted stage of one of
the motile Dinoflagellates (Pyrrhophyta).
Unless other species are shown to be
separable and distinctive, the genus may
be reduced to synonymy.

Figure 124

170b Cells centrally placed in a sheath which has few or no lamella-
tions; pyrenoid present; (usually colonial, sometimes solitary). See
Fig. 41 GLOEOCYSTIS

171a (169) Chloroplast 1; cells solitary (often gregarious) 172

171b Chloroplasts more than 1; (cells usually ellipsoid in a gregarious
association but sometimes round). Fig. 125. PALMELLOCOCCUS

Figure 125

Fig. 125. Palmellococcus miniatus (Kuetz.) Chod. a, habit of colony;
b, portion of colony showing cells with Chlamydomonas-\ike chloro-
plast.

These oval or spherical cells usually occur as films on moist sub-
strates (rocks, cement walls, etc.). There are 1 to several chloroplasts
without pyrenoids. Reproduction is by the formation of autospores
(Chlorococcales). Identification is difficult unless the organisms are
cultured because there are so many minute green cells which might
be confused with th^s genus.

82

HOW TO KNOW THE FRESH-WATER ALGAE

172a Cells associated to form an extended stratum on trees, wood,
stones. See Fig. 66 PROTOCOCCUS (PLEUROCOCCUS)

172b Cells not forming such a stratum 173

173a Chloroplast a thin layer along the wall; pyrenoid usually lack-
ing; free-living or in tissues of animals (sponges, etc.), reproduc-
ing by autospores (replicas of the adult cell). See Fig. 91

CHLORELLA (ZOOCHLORELLA)

173b Chloroplast a massive cup with a pyrenoid; on damp aerial sub-
strates; reproducing by zoospores. See Fig. 42

CHLOflOCOCCl/M

174a (167) Cells oval, ovate, or irregular globose, with thick-layered
walls bearing knobs and protrusions 175

174b Cells without thick walls and knob-like protrusions 176

175a Chloroplasts numerous, parietal, cone-shaped. Fig. 126

EXCENTROSPHAERA

Fig. 126. Excentrosphaera viridis G.
T. Moore.

This is the only species reported
for the genus. It is found in the
water or in very wet soil and is
identified by its irregular shape pro-
duced by a lamellated thickening of
Fl9ure 126 the wall in one or more places. The

chloroplasts are cone-shaped and all
are directed inwardly from their parietal position along the wall.

83

HOW TO KNOW THE FRESH-WATER ALGAE

175b Chloroplast a massive, axial body with processes which are flat-
tened against the wall. Fig. 126V2 KENTROSPHAERA

Fig. 126V2. Kentrosphaera Bristolae G. M. Smith.

There are 2 or 3 species of this genus (often
included in the genus Chloiochytrium (Fig. 94)
but only K. Bristolae has been reported from
this country. The cells are similar in shape
but have a free-living habit, usually occurring
in damp soil.

Figure 12614
176a (174) Cells with spines 177

176b Cells without spines 179

177a Spines distributed over the cell wall 178

177b Spines localized at the poles or at the midregion of the cell. See
Fig. 118 LAGERHEIMIA (CHODATELLA)

178a Spines shorter than the diameter of the cell. See Fig. 120

BOHLINIA

1 78b Spines needle-like, as long as or longer than the diameter of the
cell; cell solitary or in 2's. See Fig. 73 FRANCEIA

179a (176) Cells with spiral, longitudinal ribs on the walls. Fig. 127.
SCOTIELLA

Fig. 127. Scotiella nivalis (Chod.) Fritsch.

This genus contains a number of species, most of
which have been collected in the flora of red snow
at high altitudes. Differences lie in the shape of the
cell and the type of ridged decorations on the wall.
Occasionally Scotiella species are collected in the
tychoplankton at low altitudes. Some authorities place
this genus in the Volvocales because of the type of
chloroplast and the evidence of basal-distal differen-
tiation in the cell; whereas others include it with the
Chlorococcales.

Figure 127

84

HOW TO KNOW THE FRESH-WATER ALGAE
179b Cells without longitudinal ribs 180

180a Cells small, less than 4.5 ,l long, with a plate-like chloroplast at
one end. See Fig. 116 NANNOCHLOR1S

180b Cells relatively large, without such a chloroplast 181

181a Two or more masses of dark mucilage appearing at either end or
on either side of the cell; usually 2-4 cells in a common invest-
ment, but often solitary. See Fig. 83 GLOEOTAENIUM

181b Without dark masses of mucilage about the cells 182

182a Cells oval, often solitary but usually gregarious, forming an ex-
panse on moist aerial substrates. See Fig. 125

PALMELLOCOCCUS

182b Cells lemon-shaped oval or ellipsoid (usually several together in
old mother-cell wall, but may occur solitary); aquatic. See Fig.
85 OOCYSTIS

183a (155) Cell body actually spherical but with 4 long, narrow, brown
arm-like appendages radiating from it. Fig. 128. PACHYCLADON

Fig. 128. Pachycladon umbrinus G. M. Smith.
(Redrawn from Smith.)

This rare plant (one species in the genus) oc-
curs in the euplankton of lakes. The long, dark-
ly colored appendanges from a relatively small,
subspherical cell body make it easy of identifi-
cation.

Figure 128

85

HOW TO KNOW THE FRESH-WATER ALGAE
183b Cell shaped differently, or not with such appendages 184

184a With several long spines forming a tuft at the angles of the cell.
(See Polyedriopsis quadrispina, however) at the angle of the cell.
Fig. 129 POLYEDRIOPSIS

Fig. 129. Polyedriopsis spinulosa G. M.
Smith.

There are 2 species in this genus,
both of which are euplanktonic. They
are rectangular or polyhedral in shape
Figure 129 with from 1 to 4 long spines at each

angle. P. quadrispina G. M. Smith
has but 1 stout spine at each angle; is quadrate in shape.

184b With 1. 2, or 3 spines, or without spines at the angles of the
cell 185

185a Without spines 186

185b With 1-3 spines at the angles 187

186a Body of the cell gradually narrowed at the angles to form horn-
like, twisted processes. Fig. 130 CERASTERIAS

Fig. 130. Cerasterias irregulare G. M. Smith.

There is apparently only 1 good species in
this genus which is characterized by having ir-
regularly triangular cells with twisted processes.
Occurs in the euplankton. Should be compared
with Tetraedron (Fig. 131).

Figure 130

86

HOW TO KNOW THE FRESH-WATER ALGAE

186b Body of the cell abruptly narrowed to form horn-like processes.
Fig. 131 TETRAEDRON

Fig. 131. a, Tetraedron limneticum
Borge; b, T. asymmetricum Presc; c,
T. lobulation var. crassum Presc; d,
T. regulare var. granulaium showing
chloroplast; e, T. regulare var. granu-
latum Presc; f, T. regulare var. bi-
furcatum Wille.

This genus contains a large number
of species which vary considerably in
their shape and in the number of arms
Figure 131 or processes. Whereas some are sim-

ple and have rounded angles, others
are polyhedral in shape and have varying degrees of lobings at the
angles. They occur both in the euplankton and in the tychoplankton.

187a (185) Cells with 1 spine at each angle

188

187b Cells with 2 or 3 spines at the angles. Fig. 131b. . .TETRAEDRON

188a Spines slender and needle-like. See Fig. 129. . .POLYEDRIOPS1S

188b Spines broader at the base and stout, decidedly tapering. Fig.
132 TREUBARIA

Fig. 132. Treubaria crassispina G. M. Smith.

This free-floating plant is similar to Pachy-
cladon (Fig. 128) but the processes are not
darkly colored and are not toothed at the tip.

Figure 132

87

HOW TO KNOW THE FRESH-WATER ALGAE

189a (35) Plant a microscopic unbranched filament, attached or free-
floating: or a macroscopic thallus in the form of an expanded
sheet, a tube, or an arbuscular (tree-like) gelatinous and beaded
growth 190

189b Plant a branched filament, a coenocytic tube (without cross walls)
or an attached cushion or disc in which the branching habit is
obscure because of closely oppressed branches 241

190a Cells constricted in the midregion, with 2 large chloroplasts, one

in either 'semicell' 191

(In some species of filamentous desmids the constriction is very
slight, being only a slight invagination or concavity of the lateral
walls. See illustrations of Hyalotheca, Fig. 137, and of Gymnozy-
ga. Fig. 136 before proceding in the key.)

190b Cells not constricted in the midregion 198

191a Cells adjoined by the interlocking of short, straight, horn-like or
hooked processes at the poles 192

191b Cells adjoined by their end walls, either along the entire apical
surface, or at the ends of arms which project from the apex. . 194

192a Interlocking polar processes simple, slender and horn -like. Fig.
133 ONYCHONEMA

Fig. 133. Onychonema laeve var.
latum West <£ West.

There are 2 rather common spe-
cies of this filamentous desmid
genus. O. tiliioime (Ehr.) Roy <&
Biss. has the lateral angles ot

Figure 1 33 .

the semicells furnished with a
spine and the polar processes are
relatively long. O. laeve Nordst. has cells without lateral spines and
appears like a small Cosmaiium (Fig. 113) in a filament, the cells ad-
joined by short (sometimes scarcely evident) polar processes.

88

HOW TO KNOW THE FRESH-WATER ALGAE
192b Interlocking polar processes not slender and horn-like 193

193a Interlocking processes in the form of forked lobes which bear
recurved hooks. See Fig. 110 MICRASTER1AS

193b Interlocking processes simple, short and tuberculate. Fig. 134.
SPHAEROZOSMA

Fig. 134. Sphaerozosma excavata
Ralfs.

This is a filamentous desmid in
which the cells are adjoined by
the interlocking of the polar pro-
cesses themselves. None of the
Figure 134 species bear spines but they usu-

ally have minute granules at the
angles of the semicell, or forming transverse bands across the semi-
cell. This genus usually occurs in acid lakes, intemingled with other
desmids.

194a (191) Semicells transversely elliptic or oval, the median incision
of the cell deep. Fig. 135 SPONDYLOS1UM

Fig. 135. Spondylosium sp.

Although this genus can have
Figure 135 cells that are triangular in end

view, most species have cells, that
are compressed and are somewhat like Cosmarium (Fig. 113) in a
filament. One species which is rather rare is S. pulchrum (Bail.)
Archer. It has semicells which are much extended laterally so that
the cell is much wider than long. The apices of the cells in this
are furnished with a protrusion which adjoins that of the adjacent
cells in the filament. The walls are smooth and undecorated.

194b Semicells not transversely elliptic, median incision not deep,
sometimes only a slight concavity of the lateral wall 195

195a Cells cylindrical, subcylindrical, or barrel-shaped 196

195b Cells quadrate or angular, usually with the margins conspicuous-
ly lobed. (See Fig. 138b, Desmidium Bailey i, however) 197

89

HOW TO KNOW THE FRESH-WATER ALGAE

Figure 136

196a Cells barrel-shaped, with a slight notch-like median incision in
the broadest part of the cell where it is somewhat bulged. Fig.
136 GYMNOZYGA

Fig. 136. Gymnozyga moniliformis Ehr.
There are 3 species of this genus
found in the United States, differenti-
ated mostly on the size and propor-
tions of the cell, but none are as com-
mon as the one illustrated. This species
occurs sometimes almost pure in pools within Sphagnum bogs, and is
a common component of the desmid flora of almost any soft or acid
water habitat. G. moniliformis is characterized by having barrel-shaped
cells that have longitudinal striations in the apical portion of the
semicells. These are sometimes faintly seen, especially in living cells
when the chloroplast obscures them.

196b Cells cylindrical or somewhat rectangular, with a broad and
shallow emargination rather than an incision in the midregion.

Fig. 137 HYALOTHECA

(See also Desmidium Bailey i. Fig. 138b.)
Fig. 137. Hyalotheca dissiliens (Smith)
Breb.

There are 3 or 4 common species of this
genus, differentiated by cell shape and
Figure 137 proportion, some being short and nearly

quadrate whereas others are cylindrical.
In some individuals the constriction of the cell occurs only as a shallow
invagination in the median part. In Sphagnum bogs small pockets of
water or pools in the mat may be densely green with a pure growth
of H. mucosa (Dill.) Ehr., a species which has a conspicuous gelatin-
ous sheath.

197a Cells wider than long or as wide as long, without a median in-
cision or with but a slight median notch; walls at the poles of

young semicells infolded or replicate . Fig. 138 DESMIDIUM

Fig. 138. a, Desmidium Gievillii
(Kuetz.) De Bary; b, D. Baileyi
(Ralfs) Nordst.

Cells of this filamentous desmid
genus vary much in shape. Some
are oval and moniliform when
seen in end view, some are tri-
angular, and some are quadran-
gular. The shape of the cell may
be determined by careful focusing
up and down through the depth of a specimen. A characteristic habit
of some species is to show a spiral twisting of the cell arrangement
so that in any one view they do not have their processes in the same
plane throughout the length of the filament. Desmidium usually oc-
curs in the same habitats with Hyalotheca (Fig. 137).

90

Figure 138

HOW TO KNOW THE FRESH-WATER ALGAE

197b Cells a little longer than wide, rectangular, with a narrow median
incision; 4-lobed in end view; poles of young cells infolded. Fig.
139 PHYMATODOCIS

Fig. 139. Phymatodocis Nordstedti-
ana Wolle.

Although rarely found this fila-
mentous desmid may be the domi-
nant form in some habitats that are
especially favorable. The cells ap-
Figure 139 pear somewhat quadrangular when

seen in front view (as they occur
in the filament) but are quadrilaterally symmetrical and are 4-lobed
as seen in end view.

198a (190) Chloroplast parietal, of various shapes,
net-like, ring-like, or plate-like, with pads and
thin areas (Fig. 139 l A): or ii axial, plants in
the form of a macroscopic thallus as in Fig.
153 210

Figure 139'/4

198b Chloroplast axial, a broad band, or star-
shaped; if parietal, in the form of a ribbon
as in Fig. 139 1 /2,* microscopic 199

gg l^^l^^ j

f O

Figurr 139%

(The following genera are determined with difficulty when in the
vegetative condition alone; reproductive structures and 'fruiting' stages
are often necessary for completely satisfactory identification.)

199a Chloroplast 1 or 2 in a cell; stellate, with radiating processes from
a central core which includes a pyrenoid 200

199b Chloroplasts other shapes.

203

91

HOW TO KNOW THE FRESH-WATER ALGAE

200a Cells quadrate, with 1 star-shaped chloroplast containing a single
pyrenoid. Fig. 140 SCH1ZOGONWM

Fig. 140. Schizogonium
murale Kuetz.

This species and 1 oth-
er, S. crenulafum (Kuetz.)
Gay with short, crinkly
filaments, are found in
the United States, grow-
ing on dripping rocks, or wet soil. The basically filamentous habit
may become expanded so that a frond-like thallus is produced. This
genus, together with Prasiola (Fig. 153) have sufficient structural and
reproductive characteristics to warrant placing them in a separate
family (Schizogoniaceae) and order (Schizogoniales). The star-shaped
chloroplast is helpful in making determinations.

Figure 140

200b Cells mostly longer than wide; 2 chloroplasts 201

201a Chloroplasts 2-6 relatively small and biscuit-shaped or somewhat
star-shaped, connected in the midregion of the cell by a strand
of cytoplasm inclosing the nucleus; conjugating cells becoming
filled with layers of pectic substance; zygospores cushion-like,

compressed spheroid, or subquadranguler. Fig. 141

ZYGNEMOPSIS

Fig. 141. a. Zygnemopsis decus-
sate* (Trans.) Trans., vegeta-
tive cells with cushion-like
chloroplasts; b, conjugation
to form zygospores; c, Z. des-
midioides (West & West)
Trans.

The differences between this
genus and Zygnema occur

Figure 141

mostly within the reproductive
habit so that determination of
plants in the vegetative condi-
tion is not certain. The irregu-
lar, biscuit-shaped chloroplasts are not conspicuously star-shaped as
they usually are in Zygnema, a genus which is more commonly found
and which includes more species than does Zygnemopsis.

92

HOW TO KNOW THE FRESH-WATER ALGAE

Figure 142

201b Chloroplasts diiferent in shape, or if star-shaped, larger than
above, and always 2; conjugating cells not becoming filled with
pectic substances; zygospores globose, compressed globose, or
oval 202

202a Chloroplasts 2, definitely star-shaped, each containing a large
central pyrenoid; aquatic. Fig. 142 ZYGNEMA

Fig. 142. Zygnema pectina-
tion (Vauch.) C. A. Agardh,
vegetative cells showing
star-shaped chloroplast.

There are numerous spe-
cies of Zygnema, differenti-
ated on the basis of t he
zygospore morphology. The
paired, star-shaped chloro-
plasts in each cell make identification of the genus reasonably cer-
tain. Frequently the cells ere so densely packed with starch grains
and cytoplasmic granules that the shape of the chloroplast is difficult
of determination. Application of an iodine solution often facilitates
observation, or if one examines several lengths of filaments under low
magnification the stellate form of chloroplasts will become apparent.
A few species have a conspicuous gelatinous sheath.

202b Chloroplasts axial as above but with radiating processes much
reduced, sometimes bridged so as to form a dumb-bell shaped
mass; terrestrial. Fig. 143 ZYGOGONIUM

Fig. 143. Zygogonium eri-
cetorum Kuetz.

These filaments are
somewhat irregular be-
cause the cell walls are
unevenly thickened and
usually are invested by
a layer of mucilaginous
substance. The cells have
the habit of putting out frequent rhizoidal protrusions which may
branch. Sometimes the conjugation tubes (when they fail to meet
other tubes) will continue to grow as rhizoidal processes. The plant
is usually found in aerial or subaerial habitats (occasionally in the
water on submerged stumps, etc.).

Figure 143

203a (199) Cell sap purplish 204

203b Cell sap not purplish 205

93

HOW TO KNOW THE FRESH-WATER ALGAE

204a With 2 disc-like chloroplasts. Fig. 144 PLEUROD1SCUS

Fig. 144. Pleurodiscus purpureus
(Wolle) Lag., showing disc-like
chloroplasts.

There is but one species of this
Figure 144 genus reported thus far from the

United States. It is a plant easily
identified by its unique, plate-like chloroplasts and purple cell sap.

204b With 1 band-like chloroplast. Fig. 145 MOUGEOTIA

Fig. 145. a, Mougeofia gen-
uflexa ( D i 1 1 w . ) C. A.

Agardh, showing genicu-
late or 'knee-bending' type
of conjugation and the
plate-like axial chloroplast;
b, M. elegantula Wittr., zy-
gospore with residues in
conjugation cells; c, M. sp.,

showing rhizoidal branch-
Figure 145 gg

Like Spirogyra (Fig. 147) there are many species of Mougeotia
separable by zygospore shape and wall markings. Most species have
a relatively wide, band-like chloroplast containing a row of large
pyrenoids. The chloroplast (axial) is capable of rotating within the
cells so that the band, when seen on edge, appears as a narrow
ribbon. The shifting of the chloroplast is supposed to be a response
to the direction of more favorable illumination.

205a (203) Chloroplasts in the form of spiral ribbons, with many pyre-
noids 206

205b Chloroplasts axial bands or plates; pyrenoids 2 to several.. 208

206a Cell wall densely and minutely granular. See Fig. 106

GENICULARIA

206b Cell wall smooth 207

94

HOW TO KNOW THE FRESH-WATER ALGAE

207a Chloroplasts nearly parallel, only slightly twisted; conjugation
without the formation of tubes. Fig. 146 S1ROGON1UM

Fig. 146. Sirogonium sticticum (Engl. Bot.)
Kuetz., showing parallel chloroplasts.

This genus is differentiated from Spirogyra
(Fig. 147) on the shape and arrangement
(nearly straight and parallel) of the ribbon-
like chloroplasts, and (in reproductive ma-
Figure 146 terial) by the absence of a conjugation tube

between the cells of adjoined filaments.
There is geniculation of filaments to bring the conjugating cells into
juxtaposition.

207b Chloroplasts definitely spiralled; conjugation by the formation
of tubes from one or both cells, either between cells of two dif-
ferent filaments (scalariform conjugation), or between adjacent

cells in the same filament (lateral conjugation). Fig. 147

SPIROGYRA

Fig. 147 a, Spirogyra ihizobrachiales
Jao, showing rhizoidal branches
and conjugation; b, zygospore; c,
S. aequinoctialis G. S. West; d, cell
showing chloroplasts and numer-
ous pyrenoids.

This is the most commonly found
member of the entire order of Zygne-
matales. There are numerous spe-
cies differentiated on the morpholo-
gy of the zygospore, number of chlor-
oplasts, and size. Chloroplasts alone,
and size of cell do not distinguish
species in this genus, and identifi-
cation of vegetative material cannot
be made. Spirogyra forms green
'clouds' of cottony growths, usually
in guiet water. In the reproductive
state the plants appear at the sur-
face, forming cottony mats ('pond scums') and become brown or 'dirty'
colored.

Figure 147

95

HOW TO KNOW THE FRESH-WATER ALGAE

208a. (205) Chloroplasts without pyrenoids. Fig. 148

MOUGEOTIOPSIS

Fig. 148. Mougeotiopsis calospora
Palla. a, vegetative cells with plate-
like chloroplast (without pyrenoid);
b, zygospores.

There is only 1 species of this
genus reported from the United
States, and it is very rare. It is pos-
sible to make tentative identification
of the species in the vegetative state
because the chloroplast is much like that of Mougeofia, but without
pyrenoids. The cells are characteristically very short cylindric. In
reproduction it is similar to Debarya (Fig. 149) in that the entire con-
tents of the conjugating cells become fused to form the zygospore.

Figure 148

208b Chloroplasts with 2 to several pyrenoids

209

209a Filaments slender, mostly under 12 li in diameter (rarely as much
as 30 [X or 42 jx): chloroplast a parietal plate, usually not filling
the cell; conjugating cells becoming filled with pectic substances;
granular residues not found in the emptied reproductive cells;
plants rare. Fig. 149 DEBARYA

Fig. 149. Debarya sp., showing
formation of zygospores and the
lamellated substance deposited
in the conjugating cells.
Species of Debarya are like

some of the slender species of

Mougeotia and cannot be differ-
entiated in the vegetative condi-
tion. Debarya is much less frequently found than Mougeotia. In repro-
duction all of the contents of the conjugating cells enter into the forma-
tion of the zygospore and the space once occupied by the protoplasts
becomes filled with lamellated substance which is light refractive.

Figure 149

209b Filaments usually wider; chloroplast a broad, axial band with
conspicuous pyrenoids, filling the cell laterally (in most species)
but not in length; conjugating cells not filled with pectic sub-
stances; granular residues present in the emptied reproductive
ceUs; plants common. See Fig. 145 MOUGEOTIA

96

HOW TO KNOW THE FRESH-WATER ALGAE

210a (198) Plant a cluster of short, erect filaments (usually is branched
but sometimes appears unbranched when young; some species
form attached discs). Fig. 150 COLEOCHAETE

Fig. 150 a, Coleochaete Nitellaium
Jost; b, C. soluta (Breb.) Pringsh.;
c, C. orbicularis Pringsh.
There are 4 or 5 species of this
genus which are commonly found
in this country. They are differ-
entiated by habit of growth (pros-
trate or in cushion-like tufts) and
by size of cells. One species, C.
Nitellarum Jost, occurs only in the
walls of Nitella (Fig. 3) and is
nearly always found wherever the
host plant occurs. The endophyte
shows especially well when Nitel-
la is allowed to deteriorate in a
Figure 150 laboratory container. The sheathed

seta which characterizes Coieo-
chate arises from a granule (the blepharoplast) within the cell and
emerges through a pore in the wall. The disc-like thallus formed by
some species of Coleochaete is frequently found on the sides of glass
aquaria. In nature they occur on other algae or on submerged stems of
cattail, or on submerged glass and crockery.

210b Plant not in the form of a cushion of erect filaments 211

211a Thallus a macroscopic expanded sheet, one cell in thickness
(usually in salt water, but occasionally found in brackish and
fresh water); attached at one end. Fig. 151 MONOSTROMA

Fig. 151. Monostroma latissimum (Kuetz.) Wittr.

In salt water this genus includes species which
form large thalli many centimeters long and wide,
whereas in freshwater the plants are much smaller.
Salt water species- are sometimes carried inland
and become distributed when oyster shells are
thrown into fiesh water habitats.

Figure 151

211b Thallus not a large, flat sheet, not so attached.

212

97

HOW TO KNOW THE FRESH-WATER ALGAE

212a Thallus an mtestiniform, hollow tube, with the wall one cell in
thickness. Fig. 152 ENTEROMORPHA

Fig. 152. Enteromorpha intestinalis (L.)
Grev. a, habit of branched thallus; b,
cells showing parietal position of chloro-
plasts.

Like Monostroma (Fig. 151) Enteromorpha
is primarily a marine alga but becomes
adapted rather easily to freshwater habi-
tats. The long, hollow tubes are frequently
branched, forming slender threads or crin-
kled tubes. The plants are always at-
tached to submerged plant stems, or to
stones, especially in flowing water. There
are eight species known from freshwater
or brackish situations.

212b Thallus not an intestiniform tube 213

213a Plant a lobed or ruffled disc of cells, 10 cm. or less across; at-
tached by a central short stipe (usually on rocks in alpine and
arctic situations). Fig. 153 PRASIOLA

Fig. 153. Prasiola crispa (Lightf.) Menegh. a,
several forms of thallus; b, diagram to show

-jxfob 00 op 00 /~) cells in 4 ' s -

00 00 ®*-L®° L( Four species of Prasiola have been re-

^00 00 QO j) j^ ported from the United States, mostly from

^g-j-o- ^ ^^^/ P )/ alpine and subalpine situations. In the Arctic

^^^y ^V // me plants are common on soil rich in nitro-

a genous wastes. The thalli are foliose or

Fiqure 153 frond-like sheets, attached at a central point

by a short stalk or disc. The genus and

Schizognium (Fig. 140), comprising the Schiz-

ogoniaceae, have star-shaped, axial chloro-

plasts.

213b Plant otherwise; a filament or a gelatinous strand 214

214a A filament of cells 221

214b A gelatinous strand, or a tube, or a plant including a gelatinous
tube which may or may not have cross partitions 215

98

HOW TO KNOW THE FRESH-WATER ALGAE

215a Thallus a tube-like strand (sometimes forked), containing many
lamellations (layers); cells at the tips of the tubes. Fig. 154...

HORMOTILA

:X\V\'\\'\ \

Fig. 154.
Borzi.

Hormotila m ucigena

Figure 154

This curious plant is a branched
colonial form by virtue of the fact
that as the cells divide they se-
crete mucilage and construct gelatinous strands that branch and re-
branch, the cells always occurring at the distal ends of the strands.
The plant (one species only being known) is classed near Gloeocystis
(Fig. 41) in the Tetrasporales (Palmellaceae).

215b Thallus not as above 216

216a Cells located at the ends of undivided tubes, the cell bearing a
seta with a sheathed base. See Fig. 62. . .CHAETOSPHAERIDIUM

216b Cells without setae 217

217a Cells constricted in the middle, occurring at the ends of tubes
which are united in colonies that are impregnated with lime. Fig.
155 OOCARD1UM

Fig. 155. Oocardium stratum Naeg.

This is a very rare desmid, or at least it
has been reported but few times, probably
because it is overlooked by collectors. The
Cosmarium-like cells occur in colonies at
the ends of branched gelatinous strands and
are inclosed in a firm sheath of lime. They
are to be sought on encrustations of rocks in
dripping or flowing water.

Figure 155

217b Cells not constricted in the midregion, not arranged as above. .218

99

HOW TO KNOW THE FRESH-WATER ALGAE

218a Cells in tubes which are attached to microfauna. See Fig. 64.
COLACIUM

218b Cells not attached to microfauna 219

219a Cells elongate-oval; brackish water or marine. Fig. 156

PRASINOCLADUS

Fig. 156. Prasinocladus lubricus Kuck.

Although essentially marine this species has been
known to occur in brackish water. It is an attached,
branching tube composed of a series of compartments,
forming a tree-like thallus, in which the oval proto-
plasts occur only at the tips of the branches. There
is one chloroplast at the forward end of the cell which
actually is the posterior pole because like some of its
relatives (Malleochloris, Fig. 95) the cells are in an
inverted position with the anterior end downward.

Figure 156

219b Cells round, not in brackish water habitats

220

220a Cells in 1 series or in several irregular series within simple or

branched tubes; chloroplasts 2 laminate. See Fig. 45

PALMODICTYON

220b Cells in several series, arranged in clusters of 4 in an irregularly
shaped, elongate strand of mucilage; chloroplast 1, a parietal cup.
See Fig. 35 TETRASPORA

100

HOW TO KNOW THE FRESH-WATER ALGAE

221a (214) Filament of cells in 1 series, at least in the basal portion.

222

221b Filament of cells in more than 1 series, at least in the upper

.239
portion *""

222a Filament of cells in 1 series in the basal portion, of several series
in the upper. Fig. 157 SCHIZOMERIS

Fig. 157. Schizomeris Leibleinii Kuetz. a, base
of filament and uniseriate portion; b, multi-
seriate upper portion of filament.

There is but 1 species in this genus, a
plant which is uncommon but widely dis-
tributed over the world. The filaments are
relatively large, when fully developed, and
rather coarse. They occur in dark green
clumps in standing water and have the macro-
scopic appearance of a growth of Spirogyra
(Fig. 147) or of some large Ulothrix (Fig. 167),
but unlike these genera, Schizomeris fila-
ments separate easily and can be seen in-
dividually within the tuft. There is some evi-
dence that the plant . favors water rich in
nitrogenous matter and is to be looked for
in shallow water of lakes near the entrance
of drains, effluent of sewage treatment plants,
etc.

Figure 157

222b Filaments of cells in 1 series throughout

223

223a Chloroplast a parietal network, usually close and dense, cover-
ing the entire wall; pyrenoids many and conspicuous 224

223b Chloroplast otherwise; pyrenoids few or lacking

225

101

HOW TO KNOW THE FRESH-WATER ALGAE

Figure 158

224a Cells cylindrical, usually many times their diameter in length

(sometimes only 3 times longer than wide); wall thick. Fig. 158.

RHIZOCLONIUM

Fig. 158. Rhizoclonium Hookeri Kuetz.

The species belonging to this genus are all
coarse, wiry, and but very little (if at all)
branched. The filaments are composed of rela-
tively long, cylindrical cells with thick walls
which frequently show lamellations, especially
near the cross walls. There are numerous
chloroplasts, often compactly arranged and dif-
ficult of determination in respect to shape and
organization. There are many pyrenoids. The
branches are usually short and mostly at right
angles to the main axis, but when they are long
these plants intergrade with some forms of
Cladophora (Fig. 192), in which the branching
habit has been reduced. Rhizoclonium forms
dense, tangled filamentous mats in standing
water, or long, stringy, sometimes rope-like
strands in flowing water. R. hieroglyphicum (Ag.) Kuetz. is the most
common species, one which has rather uniformly cylindrical cells with
relatively thin walls, and does not branch.

224b Cells not cylindrical, slightly larger at the anterior end, or even
when appearing cylindrical always with at least 1 ring-like scar

at the anterior end just below the cross wall. Fig. 159

OEDOGONIUM

Fig. 159. a, Gedogonium crispum Kuetz., por-
tion of filament with one fertilized and an un-
fertilized egg; b, basal hold-fast cell and por-
tion of a filament containing antheridia and
antherozoids; c, Oe. Westii Tiffany, showing
dwarf male filaments epiphytic on the female
plant.

There are over 250 species in this large genus
which belongs to a family (Oedogoniaceae) in
which there are only two other genera (Bulbo-
chaete, Fig. 195; Oedocladium, Fig. 174). Spe-
cies are differentiated by the size and morpholo-
gy of the sexual reproductive organs and by the
shape, decoration, and size of the mature zygo-
spore (oospore). Whereas some species have
the male organs (antheridia) in filaments the
same size as the female, others possess dwarf
male plants that grow as epiphytes on or near

Figure 159

102

HOW TO KNOW THE FRESH-WATER ALGAE

the female gametangium (oogonium). Oedogonium plants begin as
attached filaments and may remain so throughout life, or they may
become free-floating and form cottony masses near the surface, usually
becoming pale yellow-green or cream-colored in age. Often these
masses are so dense that if left to dry by the evaporation of water in
which they are growing they form what is known as "algae paper."

225a (223) Chloroplast a parietal plate, a ring, or a band which in-
completely encircles the cell 226

225b Chloroplast massive and dense (dif-
ficult of determination), or a parietal
sheet of thick and thin areas (padded
appearance), or a branched, beaded
thread (see MicTospora). Fig. 159 V2.
237

Figure 159%

226a Filaments composed of long, cylindrical, multinucleate units;
chloroplasts in the form of several parietal rings in each unit.
Fig. 160 SPHAEROPLEA

Fig. 160. Sphaeroplea an-
nulina (Roth) Ag.; a,
vegetative cell with
ring - like chloroplasts,
and b, one cell con-
taining fertilized eggs.

Two species of this
genus are known from
the United States, but S.
annulina is the one most
frequently seen, although it actually is a rather rare plant. Wherever
it occurs it is likely to be in abundance. The characteristic long, cylin-
drical 'cells' may be mistaken for species of Rhizoclonium (Fig. 158),
especially in the examination of preserved material. It is to be ex-
pected in shallow water of marshes and in bays of lakes.

Figure 160

226b Filaments not composed of long, multinucleate units; chloroplasts
otherwise, usually 1 in each cell 227

103

HOW TO KNOW THE FRESH-WATER ALGAE

227a Filaments prostrate, creeping on larger filamentous algae. Fig.
161 APHANOCHAETE

Fig. 161. Aphanochae-
te repens A. Br.

There are 3 species

of this genus w,hich

are very common but

are often overlooked

because of their small

size and their habit of

creeping on the walls

of larger filamentous

algae. The simple setae, with their swollen bases extending from the

cell wall are helpful in making identification. A. polychaete (Hansg.)

Fritsch is characterized by having several setae on each cell.

Figure 161

227b Filaments not creeping on algae; floating or if prostrate, with
cells in discontinuous series .... 228

228a Filaments very short (up to 20 cells); often in interrupted series.
229

228b Filaments longer, in continuous series

230

229a Chloroplast a parietal plate extended over but a small pari of
the wall; usually subaerial. Fig. 162 STICHOCOCCUS

®S3S)CZ3

Figure 162

Fig. 162. Stichococcus ba-
cillaris Naeg.
The difference between
Stichococcus and the
small filaments charac-
teristic of Hormidium (Fig.
168) is difficult to define. In the former genus the filaments are usually
relatively short (10 to 40 cells) and have a tendency to break into
short segments intermittently. Of the 6 species which occur in the
United States most are found on the bark of trees, old boards, or on
damp soil. The species illustrated is the most common, often occurring
with Protococcus on the moist bark of trees, the short filaments twisted
and contorted, or coiled hi one plane.

104

HOW TO KNOW THE FRESH-WATER ALGAE

229b Chloroplast a broad plate extended over most of the cell wall;
aquatic. Fig. 163 HORM1DIOPSIS

^*a Fig. 163. Hormidiopsis ellipsoide-

•&\ um Pres.

mirk S\ G>

j£*% Cx) % xj\$¥ ) £k This is the only species reported

O^^C/^ nfi/ from this country and possibly

A r?sa\ 7v-\ cannot be differentiated from Hor-

'^x^r^Q'Q® (&&l(w ®&. midium (Fig. 168) except that the

\jjj^ Sg$ \^AJy filaments are frequently interrupt-

1<3 ed and constricted at the joints,

Figure 163 '

the cells being oblong or oval
rather than cylindrical. Characteristically, the chloroplast extends
but only part way around the cell wall.

3S5

230a Filament composed of units which include 2 oval or subspherical
protoplasts; the space between protoplasts and the walls filled
with layered (lamellose) material. Fig. 164 BINUCLEAR1A

Fig. 164. Binucleaiia tatrana
^~ &C% T (TY& Wittr., one filament show-

ing a gelatinous sheath.

This is the only species
reported from the United
States; occurs intermingled
with other filamentous algae,

Figure 164

especially in mixtures taken from bogs. The paired protoplasts within
each unit of the filament make it easy of identification.

230b Filaments of cells without paired protoplasts as above 231

231a Filaments with a gelatinous sheath 232

231b Filaments without a gelatinous sheath 235

232a Cells cylindric-quadrate, globose or ellipsoid; adjoined at the
end walls 233

105

HOW TO KNOW THE FRESH-WATER ALGAE

232b Cells oblong, not adjoined at the end walls. Fig. 165

GEMINELLA

Fig. 165. a, Geminella in-

terrupta (Turp.) Lag.; b,

5® ^(5) ® <S> C^(S» e^Q ^^ g. mutabilis (B r e b .)

Wille.

° These are filamentous

pr^ r^\ rw^f^rw ^ f — V ^ P lants which have cylin-

drical or broadly oval
cells encased in a wide
Figure 165 sheath of mucilage. The

cells may be adjoined, or
rather evenly spaced one-half to 2 cell lengths apart. Like Hormidium
(Fig. 168) the chloroplast covers but a small portion of the wall.

233a Cells quadrate or cylindrical; cell wall in 1 piece 234

233b Cells globose, subglobose, or ellipsoid, wall usually of 2 over-
lapping pieces that meet in the midregion of the cell and form
short lateral projections (resulting from a rim about the cell in
center). Fig. 166 RADIOFILUM

(mxmxrmmmyj)

Figure 166

Fig. 166. a, Radiofilum ilavescens G. S. West; b, R. conjunctivum
Schmidle.

The globose or subglobose cells of these filaments help to separate
them from Geminella (Fig. 165) which also possesses a gelatinous sheath.
Some species (R. conjunctivum Schm., e. g.) have the wall in 2 sec-
tions which form a rather conspicuous overlapping in the mid region.
There are 3 species in this country, differentiated by shape and size
of the cells.

106

HOW TO KNOW THE FRESH-WATER ALGAE

234a Chloroplast a parietal band or ring which encircles the cell or
nearly so. Fig. 167 ULOTHRIX

"Fig. 167. a, Ulothrix
zonata (W e b e r &
Mohr) Kuetz., with
ring-like chloroplast;
b, U. cylindricum
Presc; c. U. aequal-
is Kuetz.

mrs^w^p^iw^m

Species of this genus
vary greatly in size
and proportions of the
cells. Some are short-
Figure 167 er thon wide, others

distinctly cylindrical. The most familiar species, and the largest is
U. zonata (Fig. 167a) which has a basal holdfast cell and chloroplasts
which completely encircle the cell wall. Others have a chloroplast
that forms two-thirds to three-fourths of a circle. Usually there are
1 or more conspicuous pyrenoids. Whereas most species occur in
standing water, U. zonata may be found in streams and usually in
rather cold habitats.

234b Chloroplast a laminate plate lying over a small portion of the
wall and not encircling it. See Fig. 165 GEMINELLA

235a (231) Filaments not showing a basal-distal differentiation. Fig.
168 HORMIDIUM

Figure 168

Fig. 168. Hormidium Klebsii G. M. Smitn.

This genus includes several species of simple, unbranched fila-
ments of cylindrical cells which are characterized by having chloro-
plasts which extend only part way around the cell and which are only
about one-half the cell in length.

235b Filaments with a basal holdfast,

236

107

L

Mi

M

I &!&

Figure 169

HOW TO KNOW THE FRESH-WATER ALGAE

236a Cells elongate-cylindric, the apical cell unsymmetrically pointed.
Fig. 169 URONEMA

Fig. 169. Uronema elonga-
tion Hodgetts.

This is the only species
in a genus of question-
able position. The cells
are long and cylindrical with a [/ioihrix-like chloroplast. Usually the
filament is only a few cells in length. The unsymmetrically pointed
apical cell is the chief identifying character. Young stages in the de-
velopment of Sfigeoclonium plants should be kept in mind when identi-
fication of Uronema is made.

236b Cells short-cylindric, apical cell not tapering. See Fig. 167....
ULOTHRIX

237a (225) Cells quadrate or oval to subglobose, inclosed in a strati-
fied gelatinous sheath. Fig. 170 CYL1NDROCAPSA

Fig. 170. Cylindrocapsa geminella var. minor
Hansg. a, portion of filament with oogonia;
b, vegetative cells.

Although filaments of this genus begin as
attached plants they soon become free-float-
ing and are found intermingled with other
filamentous algae, especially in soft water or
acid lakes. The chloroplasts are so dense
and the cell contents include so much food
storage material that few structural charac-
teristics can be determined. The female re-
productive organs are globular and greatly
swollen, often red in color, as are the an-
theridia which occur as series (sometimes
double) of smaller cells.

108

HOW TO KNOW THE FRESH-WATER ALGAE

237b Filaments formed otherwise

238

238a Cells orange or golden-red because of haematochrome; plants
aerial on trees and rocks; chloroplast dense and indeterminate
of shape. Fig. 171 TRENTEPOHL1A

Fig. 171. Trentepohlia Iolithus (L.) Wall-
roth, a, filament with 2 terminal spo-
rangia; b, c, sporangia in detail.

This species and T. aurea Mart, are
the 2 which are the most common of
the 6 which have been reported from
the United States. They grow on moist
stones, dripping cliffs, and on the moist
bark of trees. The characteristic orange
color makes this plant conspicuous, es-
pecially when it forms extensive patch-
es, sometimes forming a felty-mat over
large areas of rocky cliffs. In southern
United States the moist sides of trees
throughout large areas of the country-
side are colored reddish by these algae.
In humid situations of the tropics and
subtropics the filaments become infested
with a fungus to form the lichen, Coeno-
gonium. The haematochrome pigment appears in the cell as a re-
action to intense illumination.

Figure 171

238b Cells without haematochrome; plants aquatic; chloroplast a per-
forated and padded sheet or a branched, beaded ribbon. Fig.
172 MICROSPORA

Z^

Fig. 172. a, Microspore! Loeigrenii
(Nordst.) Lag.; b, M. Willeana Lag.;
c, M. floccosa (Vauch.) Thur.
In this genus the simple, un-
branched filaments have chloroplasts
that vary greatly in respect to the
degree with which they cover the
wall. There are 5 or 6 species, dif-
ferentiated by cell size and propor-
tions, and by thickness of the wall.
Some species show the 2-parted character of the wall, especially at
the ends of the filaments where the line of separation having oc-
curred in the midregion of the cell rather than at the juncture of 2
cells, forms characteristic H-shaped pieces.

Figure 172

109

HOW TO KNOW THE FRESH-WATER ALGAE

239a (221) Plants macroscopic; embedded in soft mucilage; a main axis
with whorls of branches giving the thallus a beaded effect that
is visible to the unaided eye. Eig. 173. . . . BATRACHOSPERMUM

Fig. 173. a, Batiachospermum mo-
niliforme Roth, habit of plant;
b, portion of thallus showing
small antheridial cells at tips of
branches; c, B. vagum (Roth)
Ag., antheridial branch in detail;
d, B. Boryanum Sirod., carpo-
gonial branch with 2 male cells
attached to trichogyne of the
carpogonium (female organ).

This genus belongs to the red
algae (Rhodophyta) although it
shows none of the red color char-
acteristic of this group of algae as
they occur in the ocean. The ma-
croscopic thalli, highly branched
and beaded in appearance, en-
a cased in copious mucilage make

Figure 173 these plants easily identified. The

thallus may be gray-green or blue-
green, or olive in color. B. vagum
is perhaps the most common species in this country, often occurring
in large patches over stones in flowing water. Some species prefer
quiet water and are to be sought in Sphagnum bog pools. Micro-
scopically it is one of the finest appearing genera of fresh water algae.

239b Plants microscopic, or if macroscopic, not showing whorls of
branches 240

240a Filaments uniseriate below, becoming multiseriate above with
cells brick-like in shape and arrangement; cells adjoined. See
Fig. 157 SCHIZOMERIS

240b Filaments multiseriate throughout; cells not adjoined but arranged
in irregular linear series within a gelatinous strand to form a
false filament. See Fig. 45 PALMODICTYON

110

HOW TO KNOW THE FRESH-WATER ALGAE

241a (189) Plants composed of cells or of cellular units; cross walls
present 242

241b Plants multinucleate filaments (coenocytes), without cross walls
(except when reproductive structures are developed and separated
by a cross partition from the main filament) 281

242a Plants growing on moist soil with rhizoidal branches composed
of long, narrow cells; apical cell usually with a cap (thimble).
Fig. 174 OEDOCLADIUM

Fig. 174. Oedocladium Hazenii Lewis, portion
of branched filament with an oogonium and
2 epiphytic male plants.

This genus includes but 3 or 4 species in
this country, growing on damp soil. There
may be many species in the genus but are
unknown because collections are so seldom
made from soil, and because in superficial ma-
croscopic appearance the growth may be mis-
taken for moss protonema.

Figure 174

242b Plants aquatic; parasitic on higher plants, or if terrestrial, without
long narrow rhizoidal branches and without terminal cap .... 243

243a Plants prostrate, growing horizontally; mostly epiphytic or endo-
phytic; upright branches sometimes lacking; forming discs or flat
expansions 244

243b Plants not growing entirely prostrate, at least in part with erect
branches; free-floating, parasitic on higher plants, or perforating
wood and shells 256

244a Thallus a freely-branched filament; cells usually bearing setae
or hairs 245

244b Thallus not freely-branched but forming a disc or flat expansion
of cells; sometimes forming a false cushion (pseudoparenchyma-
tous) 251

111

HOW TO KNOW THE FRESH-WATER ALGAE

245a Endophytic in walls of other algae 246

245b Not endophytic in walls of other algae 247

246a Cells bearing setae which are sheathed at the base. See Fig. 150.
COLEOCHAETE

246b Cells not bearing setae. Fig. 175 ENTOCLAD1A

.2^

Fig. 175. Entocladia polymorpha
(G. S. West) G. M. Smith.

Figure 175

This genus includes only 2
known species in the United
States. Although probably very
common it is easily overlooked
because the thalli are small and
grow inconspicuously within the
walls of larger algae.

247a (245) Some cell walls bearing setae with a sheathed base; terminal

cells of branches not tapering to form hairs. See Fig. 150

COLEOCHAETE

247b Cells with setae that are not sheathed at the base, or if without,
ends of branches tapering to form hairs 248

248a Setae and terminal hairs multicellular 249

248b Setae one-celled

250

249a Multicellular setae arising from lateral walls of the cells. Fig. 176.
PSEUDOCHAETE

Fig. 176. Pseudochaete gracilis West
<& West.

This species is rarely found, growing
partly prostrate, partly erect on sub-
merged plants or other substrates. The
branched filaments taper at both ends.
Some of the lateral branches form long,
narrow and finely tapering hairs. Some

authorities regard Pseudochaete as a form of Stigeoclonium. See Fig.

177.

Figure 176

112

HOW TO KNOW THE FRESH-WATER ALGAE

249b Multicellular hairs resulting from the apical tapering of branches.
Fig. 177 STIGEOCLONIUM

Fig. 177. a, Stigeoclonium flagelliferum
Kuetz.; b, cell showing laminate chlo-
roplast and pyrenoid.

There are several species of this
genus which are differentiated by size,
by order of branching and by the mor-
phology of the thallus as a whole, some
forming long, graceful tufts, others
more bunched growths, with part of the
thallus prostrate.

250a Growing in the mucilage of other algae. Fig. 178. . .CHAETONEMA

Fig. 178. Chaetonema
irregular e Nowak. a,
branches containing
antheridial cells; b,
oogonium.

There is only 1 spe-
cies of this genus
known, rather rarely
seen because its habi-
tat is the gelatinous
matrix of highly branched algae such as Chaetophora (Fig. 196).

Figure 178

250b Growing or creeping on the walls of larger algae. See Fig. 161.
APHANOCHAETE

113

HOW TO KNOW THE FRESH-WATER ALGAE

251a (244) Cells bearing setae with sheathed bases. See Fig. 150.
COLEOCHAETE

251b Cells without setae, or if setae present, without sheathed bases. 252

252a Endophytic in the walls of other algae. See Fig. 175

ENTOCLADIA

252b Not endophytic in the walls of other algae 253

253a Some cells bearing setae. Fig. 179 CHAETOPELTIS

Fig. 179.
Berth.

Chaetopeltis orbicularis

Figure 179

This plant forms relatively small
circular discs composed of indis-
tinctly radiating filaments closely
grown together side by side. It should
be compared with Coleochaete (Fig.
156). Almost every cell in the thal-
lus bears a long, very slender, hair-
like seta.

253b Setae lacking 254

254a Thallus a thin expansion, 1 cell in thickness; a circular disc or
a somewhat irregular expansion. Fig. 180 PROTODERMA

Fig. 180. Protoderma viride Kuetz.

This prostrate plant forms a
cushion-like thallus 1 cell in thick-
ness at the margin and one which
shows very irregular branching of
short filaments. It is to be found
growing on the stems of sub-
merged aquatic plants.

Figure 180

254b Thallus cushion-like, several cells in thickness 255

114

HOW TO KNOW THE FRESH-WATER ALGAE

255a Cells with several chloroplasts; thallus inclosed in a mucilaginous
sheath. Fig. 181 PSEUDOULVELLA

Fig. 181. Pseudoulvella americana
(Snow) Wille.

The prostrate disc-like thalli of
this plant are relatively large, 1
cell in thickness at the margin,
several cells thick near the center.
The entire plant is covered by a
gelatinous film through which an
occasional seta projects from the
cell walls, but these are rarely
found.

Figure 181

255b Cells with 1 reticulate chloroplast; thallus not inclosed in a sheath.
Fig. 182 ULVELLA

Fig. 182. Ulvella involens (Savi) Schmi-
dle (Dermatophyton) , diagram of at-
tached colony showing arrangement
of cells.

This plant forms irregular disc-like
or cushion-like growths which are sev-
eral cells in thickness when mature.
Figure 1 82 They grow on submerged aquatic plants,

sometimes on animals; do not possess setae.

256a (243) Plants parasitizing leaves of terrestrial Angiosperms (mag-
nolia, tea, etc.). Fig. 183 CEPHALEUROS

Fig. 183. Cephaleuros virescens Kunze,
diagram of thallus as it grows under
leaf epidermis of host plant, with erect
branches bearing sporangia.

This species occurs in tropical and sub-
tropical parts of the world, especially in
areas where there is an optimum humidity
so that the leaves of the plants on which
the alga is parasitic are moist. The host
may be Magnolia, tea (Thea), citrus trees,
or Rhododendron. Because of the discol-
oration and degeneration of host tissue
in the vicinity of the parasite some damage is caused by this alga and
a certain amount of economic loss results, especially in tea plantations.
Although the parasitized areas appear gray-green in color, the indi-
vidual filaments of the cushion-like thallus of the alga are usually
reddish because of the contained haematochrome pigment.

Figure 1 83

115

HOW TO KNOW THE FRESH-WATER ALGAE

256b Plants not parasitizing tissues of Angiosperms 257

257a Cells without setae; filaments not tapering to hair-like tips . . . 258
257b Cells bearing setae or with branches tapering to fine points . . 276

258a Branches short, irregular and rhizoidal, often formed only near
one end of the filament 259

258b Branches long, multicellular, usually forming a definite pattern
of growth, opposite or alternate on the main axis 261

259a Chloroplast a spiral ribbon. See Fig. 147 SPIROGYRA

259b Chloroplast not a spiral ribbon 260

260a Chloroplast an axial plate or band. See Fig. 145. . .MOUGEOTIA

260b Chloroplast a parietal network of thickenings and thin strands.
See Fig. 158 RH1ZOCLONIUM

261a Growing in wood, shells, or within limestone. Fig. 184

GOMONTIA

Fig. 184. Gomontia Holdenii Collins,
habit of thallus showing erect branch-
es.

These plants must be sought within
old wood, shells, or in limestone de-
posits. The thallus occurs as a cushion-
like, irregularly tangled mass of short
filaments from which some elements
Figure 184 grow downward to form rhizoidal pene-

trating threads. Reproductive structures
(sporangia) are borne on the upper part of the thallus or on the ends
of short erect branches. Most species are marine.

261b Not growing in wood nor in shells 262

262a Growing on trees or moist rocks; many or all cells showing an
abundance of orange or reddish-yellow pigment (haematochrome).
See Fig. 171 TRENTEPOHLIA

262b Plants growing elsewhere, not containing haematochrome 263

263a Thallus encrusted with lime 264

263b Thallus not encrusted with lime 265

116

HOW TO KNOW THE FRESH-WATER ALGAE

Figure 185

264a Thallus in the form of a cushion, giving rise to compactly ar-
ranged upright branches; cells broadest near the tip of the fila-
ments; growing on wood or shells (sometimes on other plants).

Fig. 185 GONGROSIRA

Fig. 185. Gongrosira Debaryana
Rab., horizontal and erect
branches with terminal sporangia.
Like Gomontia (Fig. 184) these
plants grow on shells and sub-
merged wood, or on aquatic
plants, but form external cushion-
like masses (often encrusted with
lime) rather than penetrating the
substrate. The erect branched
portion of the thallus is more ex-
tensively developed than in Go-
montia. The chloroplast is parietal
and usually more definite in outline than that of Gomontia which
may be padded and irregularly netted.

264b Thallus composed of loosely branched filaments, the branches
arising unilaterally. Fig. 186 CHLOROTYLIUM

Fig. 186. Chlorotylium catarac-
tum Kuetz., portion of plant
showing characteristic habit of
branch development.
The attached, lime - encrusted
thalli of this branched filamentous
plant are usually found in flow-
ing water. The filaments present
a distinctive appearance when
seen microscopically because pairs of short, green cells (often with a
reddish tinge) alternate with a more elongate and sometimes nearly
colorless cell.

265a (263) Thallus in the form of a tuft of dichotomously branched,

radiating, yellowish-green filaments. Fig. 187 LEPTOSIRA

Fig. 187. Leptosira Mediciana Borzi,
portion of plant showing horizontal
and erect branching systems.
This" species is known only from
Massachusetts and Kentucky in this
country. Filaments occur in yellow-
ish tufts and are usually attached to
subtrates in the water. The irregularly
branched filaments of bead-like or bar-
rel-shaped cells arising from a prostrate
portion of the thallus help in making
Figure 187 . identification.

Figure 186

117

HOW TO KNOW THE FRESH-WATER ALGAE
265b Thallus not a dense tuit of yellow-green filaments 266

266a Bearing enlarged, thick-walled akinetes (vegetative spores) among
the cylindrical cells of the filament, or with spores at the ends
of branches 267

266b Without akinetes 268

267a Akinetes globular. Fig. 188 CTENOCLADUS

Figure 188

Fig. 188. Ctenocladus circinnatus Borzi., showing a terminal series of
akinetes.

This is a branched filamentous species, growing epiphytically on
angiospermous plants in brackish water. The chains of globular
akinetes at the ends of branches make it distinctive, although the
habit of growth is somewhat like Gongrosira (Fig. 185).

267b Akinetes barrel-shaped or oval. Fig. 189 PITHOPHORA

Fig. 189. a, Pithophora Mooreana Collins; b, P. Oedogonia (Mont.)
Wittr., showing a sample of the chloroplast.

ek ^>

Figure 189

There are 3 or 4 species of this irregularly
branched, filamentous genus in this country, dif-
ferentiated by dimensions of the filament and by
size and shape of the much-swollen akinetes that
are formed intermittently throughout the plant.
When occurring in laboratory aquaria, having
been brought in on material obtained from bio-
logical supply houses, the filaments often fail
to develop akinetes, the cells becoming exceed-
ingly long and lose some of the appearance by
which they are usually identified.

118

HOW TO KNOW THE FRESH-WATER ALGAE

268a (266) Growing on submerged wood and stones with a prostrate
cushion-like mass of branches from which vertical branches arise.
See Fig. 185 GONGROSIRA

268b Thallus formed differently 269

269a Plants growing on shells of turtles; branching arising only from
the base of the main lilament. Fig. 190 BASICLADIA

Fig. 190. Basicladia Chelonum (Collins) Hoffman &
Tilden. a, cells at base of filament; b, branch-
ing habit; c, series of sporangia formed in upper
portion of filament.

This and 1 other species (differentiated mostly
by size) comprise the genus which is distinctive in
that the plants occur only on the shells of turtles,
especially the snapper. Old turtles are usually
"mossy" with the tufted growths of filaments which
characteristically branch so close to the base that
the branching habit is easily overlooked. Cells
may be as much as 120 fx in diameter but a milli-
meter or two in length.

269b Plant not growing on turtles, or with other types of branching. .270

270a Plants showing basal-distal differentiation, usually attached (float-
ing in age); branching arbuscular (tree-like or bush-like) 271

270b Plants not forming bushy growths 274

271a Cells with haematochrome (reddish color in the chloroplasts).
See Fig. 171 TRENTEPOHLIA

271b Cells without haematochrome 272

119

HOW TO KNOW THE FRESH-WATER ALGAE

272a Plants stout; walls thick and lamellate; chloroplast a dense reti-
culum with many pyrenoids 273

272b Plants slender, very minute (not more than 5 ^ in diameter); wall
thin; cross wall at the base of a branch above the level of origin
from the main axis. Fig. 191 MICROTHAMNION

Fig. 191. Microthamnion strictissimum Rab.

This species and its relative, M. Kuetzingianum
Naeg. are easily overlooked in collections because
the attached filaments are so minute and the chloro-
plast often so nearly colorless. They occur on
larger filaments of other organisms but usually
break away and are found floating free at ma-
turity, intermingled with other algae.

Figure 191

273a Branching open and spreading; cells mostly cylindrical. Fig. 192.
CLADOPHORA

Fig. 192. Cladophora spp. a, cell showing pari-
etal, net-like or discontinous chloroplast; b,
habit of branching.

There are numerous species of this genus
both in fresh and in salt water. They are dif-
ferentiated by size, shape of cell, and plan of
branching. The habit of branching is variable
according to habitat and species definitions,
therefore, are poorly made. Some plants exist
over winter in lakes and become wave-washed
and lose their original appearance. Other spe-
cies in lakes become free-floating and by wave
action become rolled over and over with the
result that "Ciadophora-balls" are produced.
These appear as densely branched and en-
tangle 1 growths, with cells very irregular in
shape. Perhaps the most characteristic habitat
of Cladophora is on rocks in flowing water, es-
pecially on dams and waterfalls.

120

Figure 192

HOW TO KNOW THE FRESH-WATER ALGAE

273b Branching close and entangled, often dichotomous; downward pro-
jecting rhizoidal branches common; cells irregularly swollen. Fig.
193 AEGAGROP1LA

Fig. 193. Aegaqropila profunda (Brand) Noidst.

This species is more irregularly branched
than Cladophora and has downward directed
rhizoidal branches. The upper filaments are
densely entangled and the cells are more ir-
regular in shape. As the species name sug-
gests, it is found growing on the bottom of
lakes at depths up to 200 feet (especially in
clear water). Some authorities include Aega-
gropila under Cladophora.

Figure 193

274a (270) Vegetative cells very long and cylindrical, somewhat regu-
larly interrupted by swollen, thick-walled cells (akinetes). See
Fig. 189 P1THOPHORA

274b Akinetes lacking; cells all cylindrical or nearly so 275

275a Branches scarce and short, or wanting altogether; if branches

present, without repeated branching. See Fig. 158

RHIZOCLON1UM

275b Branches many-celled, bearing secondary branches which arise
irregularly so that the arbuscular habit is almost lost. See Fig.
192; wave-washed and winter form of CLADOPHORA

276a (257) Setae without cross walls at the base, formed by lateral ex-
tensions of cells just below the anterior cross parition of the cell.
Fig. 194 FR1DAEA

Fig. 194. Fridaea torrenticola Schmidle.

This is a very rare species (the only one known
for the genus) but is quickly identified by the long,
cylindrical cells which bear thread-like extensions
that are given off laterally just below the anterior
cross wall. The filaments occur in compact tufts
and are usually yellowish-green in color.

Figure 194

276b Setae formed otherwise 277

121

HOW TO KNOW THE FRESH-WATER ALGAE

Figure 195

277a Setae bulb-like at the base. Fig. 195 BULBOCHAETE

Fig. 195. a, Bulbochaete insignis Pringsh.,
showing oogonium with oospore, and an
attached dwarf male plant; b, B. con-
gener Him; c, holdfast cell.

Like its close relative, Oedogonium (Fig.
159) this genus contains numerous species
which are differentiated on the basis of di-
mensions and details of the reproductive
structures. They cannot be identified in
the vegetative condition. The branched
filaments are always attached (at least
when young) and are quickly identified
by the bulbous-based, unicellular setae
that develop at the anterior end of the
cell. They are to be sought on overhang-
ing grass, or on the culms of rushes, sub-
merged aquatic plants, etc. Most species have dwarf male plants
growing epiphytically on the oogania (female sex organs).

277b Setae shaped otherwise , . . . 278

278a Setae sheathed at the base. See Fig. 150 COLEOCHAETE

278b Setae not sheathed at the base 279

279a Thallus not embedded in mucilage, or if so, inclosed in a very

soft watery mucilage without definite shape 280

279b Thallus inclosed in a firm mucilaginous matrix of definite shape,
globular or somewhat elongate and irregularly arbuscular (some-
times strands 4-15 cm. in length). Fig. 196 CHAETOPHORA

Fig. 196. a, Chaetophora elegans (Roth)
C. A. Ag., habit of thallus; b, C. in-
crassata (Huds.) Hazen, habit of thal-
lus; c, C. incrassata, portion of branch-
ing system.

Microscopically, species of this genus
are delicately and gracefully branched
filaments that occur in macroscopic tufts
or gelatinous balls. One, C. incrassata
(Huds.) Hazen, is composed of cables of
elongate cells which give off laterally
dense tufts of dichotomous branches.
The resulting growth produces bush-like
or arbuscular thalli which may become
10-15 centimeters in length. Other spe-
cies form spherical or irregularly glo-
bose balls one or two millimeters in
diameter on submerged leaves (especially in cold water), wood, or on
cattail stems and are often gregarious so that extensive patches occur.

Figure 196

122

HOW TO KNOW THE FRESH-WATER ALGAE

Figure 197

The firmness of the mucilage in which the plants are encased differ-
entiates Chaetophora from its relatives Draparnaldia (Fig. 197) and
Stigeoclonium (Fig. 177).

280a Thallus composed of slender, repeatedly branched filaments; cells
all about the same size but tapering to fine points or hairs. See

Fig. 177 STIGEOCLONIUM

280b Thallus consisting of an axis of large cells from which arise tufts
of branches composed of smaller cells; tufts in whorls, opposite
or alternate, occurring at rather regular intervals. Fig. 197....

DRAPARNALDIA*

Fig. 197. Draparnaldia glomerata
(Vauch.) Ag., showing tufts of lateral
branqhes, with barrel-shaped axial
cells containing band-like chloro-
plasts.

The genus is strikingly characterized
by having a filament of large cells
forming an axis from which tufted
branches of smaller cells arise. Differ-
ent species vary in size and shape of
branching tufts. The thallus is inclosed
in amorphous mucilage. Most species
occur in cold water, often in shallow
trickles or in springs. Macroscopically,
they appear as pale green gelatinous strands that easily slip through
the fingers.
281a (241) Parasitic in higher plants such as Arisaema (Indian turnip).

See Fig. 92 PHYLLOSIPHON

281b Not parasitic 282

282a Filaments repeatedly dichotomously branched, regularly constrict-
ed at the base of the forkings. Fig. 198 D1CHOTOMOSIPHON

Fig. 198. Dichotomosiphon tubero-
sus (Braun) Ernst.
This species (the only one in the
genus) occurs in dense, entangled
tufts or mats, usually on the bot-
tom of lakes, although occasional-
ly on damp soil. There are down-
ward growing, rhizoidal branches
and upward directed vegetative
Figure 198 anc j sex organ-producing branches.

The oogonia when mature are so large that they can be easily seen
with the naked eye. The plants seem to reproduce sexually only
when growing in relatively shallow water (up to 4 feet) but may
form extensive mats on the bottoms of lakes without fruiting in water
up to 60 feet in depth.

* Draparnaldiopsis is a rare genus resembling Draparnaldia but differs essentially
by having long and short cells in the main axrs (alternating). Tufts of branches are
given off by the short cells only.

123

HOW TO KNOW THE FRESH-WATER ALGAE

282b Filaments not dichotomously branched; without constrictions. Fig.
199 VAUCHERIA

Fig. 199. a, Vaucheria geminata (Vauch.)
De Cand., sex organs on a short pedicel;
b, V. sessilis (Vauch.) De Cand.

Vaucheria usually forms dark green, vel-
vety mats on damp soil,, on rocks in flow-
ing water, or occasionally wooly mats
floating at the surface of ponds, having
broken away from their substrate. At ma-
turity the growths are 'dirty' green in color.
The siphonous filaments are large enough
to be seen individually with the unaided
eye. Several species are common in fresh
water, differentiated by shape and posi-
tion of the sex organs. The mats of Vau-
cheria harbor a veritable zoological garden of small animals. Long
considered to be a member of the Chlorophyta, this genus is now
classed with the Xanthophyceae in the Chrysophyta.

283a (5) Chromatophores violet, gray-green or bluish-green, often ap-
pearing brownish in mass; mostly macroscopic Rhodophyta . . 284

283b Chromatophores yellowish-green, carotin predominating, or some
other color than above 290

284a Thallus macroscopic, spine-like, with node-like swellings, stiff and
cartilaginous, very little if at all branched. Fig. 200 . . . LEMANEA

Figure 199

Figure 200

Fig. 200. Lemanea annulata Kuetz., habit of plant.

This genus is a member of the Rhodophyta, but like other fresh
water red algae it is some other color, being gray- or olive-green.
The thalli are cartilaginous and stand erect from an attached base.
The slender, spine-like growths (up to 20 cm. in length), devoid of
branching make the plant easily recognizable. Species are differ-
entiated mostly on details of the reproductive structures.

124

HOW TO KNOW THE FRESH-WATER ALGAE
284b Thallus otherwise 285

285a Plant a uniseriate filament, branched or unbranched; (cells in 1
series); microscopic 289

285b Plant a multiseriate filament or thallus; microscopic

286

286a Thallus embedded in soft mucilage; consisting of an axial fila-
ment with cortical (overlying) cells, bearing whorls of short and
usually densely clustered branches; nodes and internodes evi-
dent. See Fig. 173 BRATRACHOSPERMUM

286b Thallus otherwise 287

287a Thallus consisting of multiaxial filaments (strands of filaments)
with numerous feathery branchings; without definite nodes and
internodes. Fig. 201 THOREA

Fig. 201. Thorea ramossisima Bory.

This is a feathery thallus macroscopically; mi-
croscopically composed of a multiaxial cable of
filaments with short, compactly arranged out-turned
branches. They may be as much as 50 cm. in
length. It is of infrequent occurrence and sexual
reproductive stages have not been found as yet.

Figure 201

287b Thallus otherwise

288

125

HOW TO KNOW THE FRESH-WATER ALGAE

288a Thallus multiaxial (cables of filaments) with closely compacted
and oppressed cortical cells; thallus branching irregularly in a
dichotomous fashion. Fig. 202 TUOMEYA

Fig. 202. Tuomeya fluviatilis Harvey, a,
habit of thallus; b, apical portion of
branch.

This rather rigid and cartilaginous mem-
ber of the Rhodophyta is identified by the
complex dichotomous or antler-like habit
of branching of the thallus which is com-
posed of multiaxial series of filaments and
corticating cells. There is but 1 species.

Figure 202

288b Thallus including a monaxial filament which is inclosed arffl sur-
rounded by compactly arranged and oppressed, polygonal cor-
tical cells which form just behind the apex. Fig. 203

COMPSOPOGON

Fig. 203. Compsopogon sp., a, habit of
thallus; b, portion of axis showing corti-
cating cells; c, apical portion of uncor-
ticated branch showing chromatophores.

This is a member of the Rhodophyta
which seldom occurs in entirely fresh
water but is frequently found in brackish
situations, attached to various substrates,
but especially to submerged stems of
woody plants such as mangrove. C. coe-
ruleus (Balb.) Mont, is the most common
species. Although essentially filamentous,
the thallus is macroscopic in proportions
and appears as a rather delicately
branched, tufted or bushy growth, blue-
or gray- to violet-green in color. It is a tropical and subtropical genus
but has been found occasionally in temperate latitudes.

Figure 203

126

HOW TO KNOW THE FRESH-WATER ALGAE

289a (285) Filaments attached, uniseriate, branched. Fig. 204

AUDOU1NELLA

Fig. 204. Audouinella vioiacea (Kuetz.)
Hamel. a, habit of thallus; b, branches
in detail.

A member of the Rhodophyta, this
species is nevertheless violet or gray-
green. The loosely branched filaments
are microscopic but may appear in tufts
of macroscopic proportions. The main
axial cells have disc-like or short ribbon-
like chromatophores. In size, form, and
habit of growth plants are easily mis-
taken for juvenile stages of Batracho-
sperum and if that genus is present in
the habitat it could be assumed that
Audouinella-\ike plants to be immature or so-called "Chantransia-stages"
of Batrachospermum rather than Audouinella. There is but 1 species
clearly defined in this country in fresh water and there is a disposition
on the part of some authorities to classify it under the genus Acrochae-
fium which is mostly marine.

Figure 204

289b Filaments attached, uniseriate, unbranched. Fig. 205 ... BANG1A

ffiQQfflBBS

Figure 205

Fig. 205. Bangia iuscopurpurea (Dillw.) Lyngb., basal portion of fila-
ment.

This is a simple, unbranched member of the Rhodophyta, greenish-
red or purplish in color. Filaments occur in tufts, sometimes dense,
attached to submerged stones and wood. Although most species of the
genus occur in salt water, this one is known from brackish or even
nearly fresh-water habitats. It may be ^expected in estuaries.

290a (283) Chromatophores yellow, yellow-brown, or dark golden-brown,
rarely blue; plants motile or non-motile 341

290b Chromatophores not yellow-brown or golden-brown 291

127

HOW TO KNOW THE FRESH-WATER ALGAE

291a Chromatophores pale yellow-green with xanthophyll predominat-
ing; iodine test for starch negative; cell contents often showing
a metallic lustre. Phylum Chrysophyta. (This group of algae is
often difficult of determination on the basis of color of the chroma-
tophore alone inasmuch as the shades of green cannot be clearly
distinguished from those of the Chlorophyta. In addition to the
iodine test for starch (which ordinarily is confirmative) heating
plants in concentrated sulphuric acid (when the specimens lend
themselves to such treatment) provides a helpful differentiation.
The yellow-green algae (Heterokontae or Xanthophyceae) become
blue-green in the acid whereas Chlorophyta remain unchanged
in color) 300

291b Chromatophores not yellow-green.

292

292a Cells with blue protoplasts or chromatophores

293

292b Cells with protoplasts or chromatophores not blue

295

293a One to four spherical or oval cells in a mucilaginous sheath which
bears a gelatinous bristle. Fig. 206 GLOEOCHAETE

Fig. 206. Gloeochaete Wit-
tiockiana Lag.

Figure 206

This

is

an anomalous
organism, the morpholo-
gy and physiology of
which is interpreted as
one of symbiotism involv-
ing a colorless member
of the Tetraspora family
(Figs. 35, 48) and a blue-
green or cyanophyceous
endophyte. The proto-
plast is a parietal cup
similar to the chloroplast
of many of the green al-
gae. The long, slender gelatinous hairs make this species easy of
identification. Cells occur in clumps (rarely solitary) attached to fila-
mentous algae.

293b Plants not as above; sheaths present or absent although cells may
be inclosed by old mother cell wall 294

128

Figure 207

HOW TO KNOW THE FRESH-WATER ALGAE

294a A linear series of globular or oblong cells within a gelatinous
matrix, chromatophores star-shaped. Fig. 207 . . . ASTEROCYSTIS

Fig. 207. Asterocystis smaiagdina
(Reinsch) Forti.

The bright blue-green, star-
shaped chromatophores of this
species (the globose or oval cells
being enclosed in a wide gelatin-
ous sheath) help to identify this
branched filamentous alga. It is
a member of the Rhodophyta; usu-
ally occurs as an epiphyte on larger filamentous algae but may appear
in mixtures of free-floating forms.

294b Two to four, or eight globose or oval cells contained within an
enlarged mother-cell wall; chromatophore-like bodies vermiform
(few and long, or many and short). Fig. 208 GLAUCOCYSTIS

Fig. 208. a, b, Glaucocystis duplex
Presc; c, G. Nostochinearum Itz.

There are apparently 2 or 3 spe-
cies of this genus which like Gioe-
ochaete (Fig. 206) involve an endo-
phytic blue-green alga and a col-
orless member of the Oocystaceae
(Fig. 85). The protoplasts are
bright blue-green and occur in dif-
ferent shapes and arrangements within either globose or oval cells,
according to species. The plants are free-floating in the tychoplank-
ton near shore or in shallow water habitats of swamps and bogs.

295a (292) Cells in compact, irregularly shaped colonies, appearing
brown or orange-colored because of dark mucilage. See Fig.
49 BOTRYOCOCCUS

295b Cells not in opague or orange-colored colonies as above; contents
red, violet-red, or green with a red tinge 296

296a Living in snow in alpine regions (red snow). See Fig. 57

CHLAMYDOMONAS

296b Not living in snow 297

297a A colony of oval or globose cells inclosed in a layered sheath.
See Fig. 41 GLOEOCYST1S

297b Cells not in colonies; sheath not layered 298

Figure 208

129

HOW TO KNOW THE FRESH-WATER ALGAE

298a Cells spherical, solitary or gregarious, terrestrial, forming dark

red patches on damp soil (common in green houses). Fig. 209.

PORPHYRIDIUM

Fig. 209. Porphyridium cruentum Naeg.

\

On the damp soil of green houses
or on wet brick walks this plant often
forms purple, or wine-red gelatinous
films. It is a unicellular member of
the Rhodophyta which has a star-shaped
chromatophore.

Figure 209

298b Cells round, ellipsoid, or fusiform, not arranged as above. . . .299

299a Cells fusiform; haematochrome coloring the green cell red; with
1 flagellum. See Fig. 8 EUGLENA

299b Cells round or ellipsoid; protoplast with a wide wall which ap-
pears as a gelatinous sheath; flagella 2, but usually not showing
when cells are in an encysted condition at which time they ex-
hibit a red color. See Fig. 19 HAEMATOCOCCUS

300a (291) Plants filamentous 301

300b Plants not filamentous 304

301a A false filament, consisting of branched tubes with 1 or 2 spherical
cells at the distal ends. Fig. 210 MISCHOCOCCUS

Fig. 210. Mischococcus confervicola
Naeg.

The globose, yellowish-green cells of
$(JD this species occur at the ends of re-
peatedly branched gelatinous stalks,
~^. attached to filamentous algae. Only 1

^©^ species is known from this country.

Figure 210

301b Plant a true filament 302

130

HOW TO KNOW THE FRESH-WATER ALGAE

302a Filament branched. Fig. 211 MONOCIL1A

Fig. 211. Monocilia viridis Gerneck.

This and another species, M. flavescens
Gerneck, are the only ones reported from
this country, the former being more com-
mon. It occurs as an irregularly and in-
definitely branched filament in soil. A
member of the Chrysophyta, the disc-like
chromatophores are yellow-green or yel-
low in color, and the food reserve is in
the form of oil; starch test negative.

Figure 21 1

302b Filament not branched 303

303a Cells long-cylindrical; wall of cells formed of 2 pieces which over-
lap at the midregion, the overlapping usually evident when empty
cells are viewed; filaments showing H-shaped pieces upon frag-
menting; cells often with lateral walls convex. Fig. 212

TR1BONEMA

-C <C? C 7 "

Q_

-xy — c=» — c? o^

.O r>> r~^ — n nn ,

■x^ c?

"C7-

^3J2§§E

Figure 212

Fig. 212. a, Tribonema bombycinum var. fenue Hazen; b, T. bomby-
cinum (Ag.) Derbes & Solier; c, T. utriculosum (Kuetz.) Hazen.

There are 3 or 4 species of this simple, unbranched filamentous
member of the Chrysophyta, differentiated by proportions of the cell
and number and shape of the chromatophores. Like Microspore! (Fig.
172) in the Chlorophyta, the cell walls are composed of 2 sections which
adjoin and overlap in the midregion of the cell. Hence when the fila-
ments fragment the typical H-shaped sections are seen. By careful
focusing the overlapping of the wall sections can be seen in the un-
fragmented portions of the filament, especially in some species which
have a relatively thick wall. The chromatophores are pale-green or
yellowish and occur as parietal discs.

131

HOW TO KNOW THE FRESH-WATER ALGAE

303b Cells short-cylindric or quadrate; overlapping of wall sections not
apparent but visible at the end of broken filaments; lateral mar-
gins of cells strictly parallel. Fig. 213 BUMILLERIA

Fig. 213. Bumilleria sicu-

gv ' -v

'■-''■■J-

v.lfttSi ■■•■

'■$*£$ .1 1& Borzi.

Figure 21 3

_ There are 2 species
known from the country,
B. exilis' Klebs being much
smaller (6 jj. in diameter)
than the one figured. The unbranched filaments are similar to Tri-
bonema (Fig. 212) but the cells are more nearly rectangular in optical
section, with parallel lateral walls. Sometimes external overlapping
H-shaped sections of thicker wall layers, brownish in color, occur inter-
mittently along the filament.

304a (300) Plant a small (1-2 mm. diam.) green vesicle, balloon-shaped;
terrestrial. Fig. 214 BOTRYDIUM

Fig. 214. Botrydium granulation (L.)
Grev.

On damp soil under green house
benches or on mud of lakes where water
has receded tiny green, balloon-like
growths appear. These are siphonace-
ous members of the Chrysophyta which
have underground rhizoidal branches
in which resting spores may be found.
Plants can be seen with the unaided
eye or are easily detected with a hand
lens. Although dark green in color the
plant has other characters which relate it to the yellow-green algae,
such as the absence of starch and the possession of zoospores with
flagella of unequal length. There is another species, B. Wallrothii Kuetz.,
which has a thick, wrinkled, lamellate wall.

304b Plant not a green vesicle; aquatic 305

305a Cells solitary or incidentally clustered 306

305b Cells in colonies, definite or indefinite in shape and arrange-
ment; sometimes forming stalked colonies 333

306a Cells attached, sessile, or on a stalk 307

306b Cells free-floating or swimming 314

307a Cells sessile 308

307b Cells on a short or long stalk 310

Figure 214

132

HOW TO KNOW THE FRESH-WATER ALGAE

308a Cell membrane in 2 sections, the upper lifting off at maturity to
allow escape of aplanospores (small globular spores); cells oval
or short-cylindric. Fig. 215 CHLOROTHECIUM

Fig. 215. Chlorothecium Pirottae Borzi.

This cylindrical plant with parietal yellow-green
chromatophores is attached by a short stalk and a disc
to submerged plants, including larger algae. It is
rather rare (only one species reported from this coun-
try) and is easily overlooked because it occurs in the
dense mixture of algae from bogs.

Figure 215

308b Cell membrane not in 2 sections 309

309a Cells globose or subglobose; cytoplasm reticulate. Fig. 216....

PERONE

v

H,

Fig. 216. Perone dimorpha Pasch-
er. a, rhizoidal stage; b, vege-
tative cell.

'.'V

A r r i

/#^°5

c

a j.^- : — •*

There is a freely moving amoe-
boid stage and an attached or en-
dophytic encysted stage in the life
history of this plant. In the resting
stage the cell is to be found in
Sphagnum or other moss leaves,
Figure 216 with a highly recticulated, faintly

pigmented protoplast.
309b Cells shaped otherwise; cytoplasm not highly recticulated nor
alveolar. Fig. 217 CHARACIOPSIS

Fig. 217. a, Chaiaciopsis acuta
(Braun) Borzi; b, C. cylindiica
(Lambert) Lemm.; c, C. spinifer
Printz.

There are several fairly common
species of this genus which occur
as epiphytes on filamentous algae.
They vary in shape and in length
of attaching stalk. Unlike the
genus Characium (Fig. 87), some
species of which are very similar
in shape, no starch is formed and

The starch-iodide

the

Figure 217

chromatophore is pale green or yellowish-green

133

HOW TO KNOW THE FRESH-WATER ALGAE

test must be used to differentiate the two genera. Characiopsis often
shows one to several spherical droplets of oil (?) or other food reserve
in the cytoplasm which are not present in Characium.

310a (307) Cells with a vase-like, pitcher-shaped or globose lorica (en-
velope) with a neck and a terminal opening. Fig. 218

STIPITOCOCCUS

Fig. 218. a, Stipitococcus vasitor-
mis Tiffany; b, S. urceolatus
West & West.

There are 3 or 4 species of this
genus of rather uncommon occur-
rence, although in particular habi-
tats the various species are rela-
tively abundant and filamentous
algae may be densely overgrown
with the epiphytes. S. urceolatus
West & West is perhaps more fre-
quently seen than others and is easily identified because of its distinc-
tive, pitcher-shaped lorica.

310b Cells without a lorica 311

Figure 218

311a Cells cylindrical, straight or curved, sometimes with a spine at
one or both ends. Fig. 219 OPHIOCYT1UM

Fig. 219. a, e, Ophiocytium parvulum (Perty)
Braun; b, O. gracilipes (Braun) Rab.; c, O.
cochieare (Eichw.) Braun; d, O. desertum
var. minor Presc.

The factors which determine the distribution

of this genus are unknown, but there seems

to be good evidence that water chemistry

determines the presence of these species, of

Cx — O^ ( which there are several reported for the

United States. Where one species is found,
^ \\ several others also occur as well as many

other genera of the Xanthophyceae, a class
of the Chrysophyta to which this genus be-
longs. Species are differentiated by presence
or absence of polar spines, and whether free-
floating or stalked and epiphytic. They usually occur intermingled
with miscellaneous algae from the shallow water of swamps and bogs,
occasionally appear in the euplankton of lakes: Most species are soli-
tary but attached forms may be incidentally colonial.

Figure 219

134

HOW TO KNOW THE FRESH-WATER ALGAE

Figure 220

311b Cells shaped differently 312

312a Cells club-shaped or somewhat pear-shaped; walls in 2 sections,

the upper lifting away to permit escape of spores. See Fig. 215.

CHLOROTHEC1UM

312b Cells spherical, fusiform, or ovoid; wall in 1 piece 313

313a Stipe slender, thread-like, longer than the cell body. Fig. 220...
PERONIELLA

Fig. 220. Peromelia Hyalothecae Gobi.

Species of this genus occur solitarily
or in gregarious clusters on other algae,
or are attached in the mucilage of co-
lonial forms. The species illustrated
seems to occur no other place but on
the filamentous desmid, Hyalotheca.
Like other members of the Chrysophyta,
the chromatophores are not a grass-
green but a pale shade, and there are
usually refractive globules of oil or some
other kind of food reserve than starch.

313b Stipe stouter, shorter than the cell body in length (or rarely equal-
ling it). See Fig. 217 CHARACIOPSIS

314a (306) With 2 flagella of unequal length. Fig. 221

CHLOHOCHHOMOJVAS

(OCHROMONAS)

Fig. 221. Chlorochromonas minuta Lewis.

This rare species (probably referrable to
Ochromonas) is variable in shape from trun-
cately-oval to pear-shaped. Care must be
used in detecting the two flagella of unequal
length. Motile, pear-shaped cells in the mi-
croscope field, with yellowish chromatophores
should be examined for flagella characters.
Frequently the cells come to rest and attach
themselves to a substrate at the posterior end.
Only one species has been reported in the United States.

314b Without flagella 315

315a Cell wall smooth 316

315b Cell wall sculptured or decorated, sometimes spiny 325

316a Cells spherical, subglobose, or broadly ovate to subpyriform (pear-
shaped) 317

316b Cells rectangular, cylindrical, or crescent-shaped 320

Figure 221

135

HOW TO KNOW THE FRESH-WATER ALGAE

317a Cells contained in a gelatinous envelope. Fig. 222

CHLOROBOTRYS

Fig. 222. Chlorobotrys iegulaiis (West)
Bohlin. a, single cell; b, two cells
inclosed in common mucilage.

The identifying character of this spe-
cies is the paired arrangement of the
spherical cells inclosed in a mucilagin-
ous sheath. There are several parietal
chromatophores and a red spot which
is an oil globule. Even though pre-
served, when some identifying char-
acteristics are lost, the cells retain the
dark-colored spot.

Figure 222

317b Cells not inclosed in a gelatinous envelope

318

318a Cell wall in 2 sections, separating and persisting as membran-
ous sections near the liberated autospores (small replicas of the
parent cell). Fig. 223 DIACHROS

Fig. 223. Diachros simplex Pascher.

This is the only species reported from
the United States. It is somewhat like
Schizochlamys (Fig. 48) in the Chlorophyta
in that the mother-cell wall fragments are
retained after new cells (autospores) are
released and these persist as hemispheri-
cal, transparent cups near the daughter
cells.

Figure 223

318b Cell wall in 1 piece; mother-cell not forming persisting sections
but degenerating to liberate spores 319

136

HOW TO KNOW THE FRESH-WATER ALGAE

319a Cells spherical. Fig. 224 BOTRYDIOPS1S

Fig. 224. Botrydiopsis arhiza Borzi.

In the same habitats where Ophiocytium
(Fig. 219) occurs one may usually find this
species; a solitary, free-floating cell which
is either spherical or spheroidal. Small cells,
when young, may contain but a single chro-
matophore, but in age develop many parietal,
yellowish-green bodies. Another species, B.
eriensis Snow, is larger and less commonly
seen. Apparently it is a truly planktonic
species whereas B. arhiza occurs in shallow
water (tychoplankton).

Figure 224

319b Cells broadly ovoid or pear-shaped. Fig. 225 LEUVENIA

Fig. 225. Leuvenia natans Gardner. (Redrawn
from Smith).

Although essentially unicellular, this spe-
cies occurs in a dense film at the surface of
a quiet pond. Young cells are spherical and
have but 1 or 2 chromatophores, whereas
older cells become pear-shaped or ovate,
and have numerous yellow-green chromato-
phores. There is but 1 species in the genus
and it seems to be rare, having been reported
only from California in this country.

Figure 225

320a (316) Cells rectangular, with a spine at each corner. Fig. 226.
PSEUDOTETRAEDRON

Fig. 226. Pseudotetraedron neglectum Pascher.

This rectangular cell with a spine at each cor-
ner clearly shows the chrysophycean character in
its 2-parted wall, the sections overlapping in the
midregion of the cell. This can be seen only when
the cells are turned on their 'side' of course. In
end view the cells are narowly elliptic. There are
several yellow-green chromatophores and oil bodies
as food reserve. The only species has been re-
ported but rarely from the United States.

Figure 226

137

HOW TO KNOW THE FRESH-WATER ALGAE
320b Cells cylindrical or crescent-shaped 321

321a Cells elongate-cylindric, coiled or S-shaped, equally rounded at
both poles. See Fig. 219 OPHIOCYT1UM

321b Cells oblong, sides convex, short-cylindric, or fusiform, sometimes
not equally rounded at both poles; curved but not coiled, nor
twisted 322

322a Cells short-cylindric, 1V2-2 times as long as broad; poles sym-
metrically rounded. Fig. 227 MONALLANTUS

^ rr ^^ •— ?v Fig- 227. Monallantus brevicylindrus

y^W^W" • ° ®k Pascher.

l$$^ : '^j&/ v 5 *-?! •-'' 7 ^his * s ^ e on ^y species reported from

Y^^^'^pW nJ£ '-<? ^ e United States. It occurs in the same

\-'-'.W^3r ^i±*S habitats with Ophiocytium (Fig. 219) and

X^>^ Bumilleriopsis (Fig. 228).

Figure 227

322b Cells fusiform or cylindric only in part; poles unsymmetrical . . . 323

323a Cells fusiform or sickle-shaped

324

323b Cells irregularly cylindrical; poles unsymmetrical. Fig. 228

BUMILLERIOPSIS

Fig. 228. Bumilleriopsis brevis Pascher.

These cells have yellow-green chromatophores
and occur singly or in clusters which are definitely
colonial. The irregularly curved cylinders (rarely
somewhat fusiform) with the poles of the cells un-
like one another in shape, help in identification.

Figure 228

138

HOW TO KNOW THE FRESH-WATER ALGAE

324a Cells broadly fusiform, abruptly narrowed at the poles. Fig. 229.
PLEUROGASTER

Fig. 229. Pleurogaster lunaris Pascher.

The chief difference between this genus and Bumil-
leriopsis (Fig. 228) is the definitely fusiform shape, the
poles of the cells symmetrical. There are 2 species,
differentiated by size and variation in shape, reported
from the United States, but like many of the genera of
Chrysophyta, they are rare and never occur in pure
growths as do so many of the Chlorophyta and Cy-
anophyta.

324b Cells narrowly fusiform, spindle-shaped or sickle-shaped. Fig.
230 CHLOROCLOSTER

Fig. 230. Chloroclostei pyreniger Pascher.

In this genus the cells are narrowly spin-
dle-shaped and usually are distinctly
curved or even sickle-shaped. They are
found intermingled sparingly among algal
mixtures from shallow water of open bogs,
and apparently only where the water is
acid. Only 1 species has been reported
from the United States.

Figure 229

Figure 230

325a (315) Cells elongate-cylindric, with a spine at one or both poles. 326

325b Cells short-cylindric, spherical or angular 327

326a Cells nearly straight or only slightly bent. Fig. 231

.CENTRITRACTUS

Figure 231

Fig. 231. Centiitiactus belanophorus Lenim., showing wall in 2 sections.

There are 3 species of the genus reported from the United States,
differentiated by size, proportions, and shape of cell. Whereas some
are very short, and elliptic when young, others are very long indeed,
and straight or slightly curved. It is the straight form that can be used
to separate this genus from Ophiocytium (Fig. 219) some species of
which it resembles in respect to the overlapping sections of the wall,
color of chromatophores, etc.

139

HOW TO KNOW THE FRESH-WATER ALGAE

326b Cells coiled, S-shaped, or hooked at one end. See Fig. 219

OPHIOCYTIUM

327a (325) Cells spherical 328

327b Cells some other shape

329

328a Cell wall serrate at the margins, the surface of the cell showing

broad depressions (sometimes faintly seen). Fig. 232

ARACHNOCHLORIS

Fig. 232. Arachnochloris minor Pascher. a,
cell showing chromatophores; b, sample of
wall showing circular, thin areas.

These round cells show the characteristic
depressions of the wall at the margin where
it appears that the cell is covered with short,
sharp spines. These are the tops of ridges
formed by slight depressions in the wall that
sometimes scarcely can be seen when the
cell is viewed in the center. There is but 1
species reported from the United States.

?<o° oOOo c Oo

Figure 232

328b Cell wall bearing curved or straight spines. Fig. 233

MERINGOSPHAERA

Fig. 233. Meringosphaera spinosa Presc.
a, optical section of cell showing chro-
matophores; b, exterior of cell show-
ing spines on wall.

In this genus the wall bears long,
or short spines or cylindrical, thread-like
outgrowths. M. spinoso Presc. question-
ably has been assigned to this genus
from freshwater ponds in this country,
although the genus is marine.

Figure 233

329a (327) Cells broadly fusiform or subtriangular, narrowed abruptly
at one or both poles to form spine-like projections. See Fig. 229.

PLEUROGASTER

329b Cells with other shapes

330

140

HOW TO KNOW THE FRESH-WATER ALGAE

330a Cells oblong to subcylindric; surface of wall with rows of depres-
sions. Fig. 234 CHLORALLANTUS

Fig. 234. Chlorallantus oblongus Pascher, rep-
resented with portion of wall removed to
show chromatophores.

The very regular rows of depressions (form-
ing teeth at the cell margin) help in the
identification of this species. The cells are
capsule-like in shape and are found scattered
about among other algae from open bogs.
Only 1 species has been reported from the
United States.

Figure 234

330b Cells with other shapes 331

331a Cells oval or biconvex. Fig. 235 TRACHYCHLORON

Fig. 235. Trachychloron biconicum Pascher.

Cells of this genus, like Chlorallantus (Fig.
234), have depressions in the wall. They are
broadly elliptic or oval or fusiform in shape
and contain a gracefully curved chromato-
phore. But one species has been reported
Figure 235 from this country.

331b Cells triangular, pyramidal, or tetragonal 332

332a Cells pyramidal or tetragonal. Fig. 236 TETRAGONIELLA

Fig. 236. Tetragoniella gigas
Pascher. a, optical section
showing chromatophores and
reticular nature of the proto-
plast; b, exterior of cell show-
ing scrobiculate wall.

The cells in this genus are
beautifully sculptured by regu-
largly arranged rows of depres-
sions. According to position
the cells show different shapes,
Figure 236 triangular or tetragonal. One

species is reported from mixtures of algae taken from open bogs.

141

HOW TO KNOW THE FRESH-WATER ALGAE

332b Cells flattened, appearing triangular in face view; fusiform in
side view. Fig. 237 GONIOCHLORIS

/SSvStt^W /^\ Fig. 237. Goniochloris sculpta Geit-

fe"^V//'°:V/^?^ / • • ^%\ !e r - a ' optical section showing

|H:::::fl:: : ::":7:^ M ■' S?S^ chromatophores; b, exterior

%(rl|||fm^^^ ff ." ""^X ' front ' view ' but fattened and
b ^^^ |B . . ,#v\ narrowly elliptic when seen from

x^'uis^^?^ fefr^ ife^ ^ e si( ^ e ' ; c ' in ^ e i Qtera ^ view ^ e

^^Sfltf^TvS^ ^^i^^-S^*^ overlapping of the 2 wall sections
^Uss*****^^ ° sometimes can be detected. There

c Figure 237 are 4 or 5 curved, plate-like chro-

matophores. One species only has been reported from the United
States.

333a (305) Cells attached by a stipe 334

333b Cells without a stipe 335

334a In a globular lorica (envelope) which has an anterior opening.

See Fig. 220 PERON1ELLA

334b Not in a lorica. See Fig. 219 OPHIOCYTIUM

335a (333) With a mucilaginous sheath 336

335b Without a sheath 339

336a Cells numerous, oval, in a globular macroscopic, free-floating

colony. Fig. 238 CHLOROSACCUS

*" ' ' ,m ■" ill. td r i—

a

Figure 238

Fig. 238. Chloiosaccus iluidus Luther (Gloeochloris Smithiana Pascher).
a, diagram of colony shapes; b, cells in mucilage.

This rare species occurs as macroscopic gelatinous balls (up to 20
mm. in diameter) on the stems of submerged plants (including Chara);
occasionally may be found free-floating. The colony is composed of
irregularly arranged oval cells containing from 2 to 6 parietal chroma-
tophores (yellow-green). There is but one species.

336b Cells shaped or arranged otherwise 337

337a Cells solitary or in pairs at the ends of branched gelatinous tubes.
See Fig. 210 MISCHOCOCCUS

337b Cells arranged otherwise 338

142

HOW TO KNOW THE FRESH-WATER ALGAE

338a Cells spherical, 2 within a globular envelope. See Fig. 222

CHLOROBOTRYS

338b Cells spherical, many within a gelatinous matrix. Fig. 239

GLOEOBOTRYS

Fig. 239. Gioeobotrys limneticus (G. M. Smith)
Pascher.

The chief difference between this genus
and Chlorobotrys (Fig. 222) is the presence of
a definite mucilaginous sheath about the cells
to form colonies. The species illustrated at
one time was assigned to Chlorobotrys; de-
scribed from the open water plankton of lakes.

Figure 239

339a (335) Cells forming loose cushions, in multiples of 2 or 4. Fig. 240.
CHLORELLIDIOPS1S

Fig. 240. Chlorellidiopsis separalibis
Pascher.

Although cells of this species are
sometimes solitary they usually occur
in closely grouped clusters on the
walls of other algae. There are 2
parietal chromatophores and at least
1 dark red oil-spot in the mature cells.
Only 1 species reported from this
country.

Figure 240

339b Cells arranged otherwise 340

340a Wall in 2 sections which separate to liberate spores (new cells)
and which persist nearby; (cells may be incidentally colonial be-
cause of gregarious habit). See Fig. 223 DIACHROS

340b Wall in 1 piece, breaking down irregularly to liberate spores;

(cells incidentally clustered to form colonies). See Fig. 224

BOTRYDIOPSIS

143

HOW TO KNOW THE FRESH-WATER ALGAE

341a (290) Plant a branched, feathery, gelatinous thallus, the proto-
plasts crowded in linear series with tough, tublular envelopes.
Fig. 241 HYDRURUS

'r*>

Fig. 241. Hy drums foeti-
dus (Vill.) Trev. Cells
in mucilaginous tubes.

<3\<£>.

Gfc O <^C^^Q* :: Usually in high moun

Figure 241

tain streams, this organ-
ism forms stringy, brown,
gelatinous masses at-
tached to stones. The
bushy, yellow-green or brown tufts contain oval cells arranged in linear
series within gelatinous tube-like strands. Sometimes a small stream
will be actually choked with the dense growths. The disagreeable odor
these plants have is responsible for the specific name. The cells may
change into rather curiously shaped, pyramidal zoospores that have
but one flagellum.

341b Plant not a feathery, gelatinous thallus 342

342a Sparsely branched, sedentary filaments. Fig. 242

PHAEOTHAMNION

Fig. 242. Phaeothamnion confervicola Lag.

This member of the Chrysophyceae is the
only genus in which there is a branched fila-
ment. The branches scarcely taper at the
ends. The plants are relatively small and
grow on the walls of larger filamentous al-
gae. Each cell has a parietal, ochre-green to
brownish chromatophore.

Figure 242

342b Not a branched filament 343

144

HOW TO KNOW THE FRESH-WATER ALGAE

343a A colony of vase-shaped cones (loricas). 1 or 2 cones arising from
within the mouth of another and forming forked series. Fig. 243.
DINOBRYON

Fig. 243. Dinobryon sertularia Ehr.

There are several species of
this genus, all of which are char-
acterized by having the motile pro-
toplasts inclosed within colorless
envelopes. The envelopes are
usually contained 1 or 2 within
another so that branching chains
are formed. Some species occur
as solitary cells, however. The
genus is one which inhabits most-
ly hard water lakes in the eu-
plankton; sometimes are very
abundant and produce disagree-
able odors and tastes in reservoirs.

Figure 243

343b Cells solitary or arranged otherwise 344

344a A unicell, consisting of a yellowish protoplast contained in a vase-
shaped envelope. See Fig. 243 DINOBRYON

344b Cells shaped otherwise, solitary or colonial 345

345a Cells solitary, colonial or filament-
ous; wall silicious and etched with
grooves or rows of dots which form
definite patterns; wall in 2 sec-
tions. 1 part forming a lid over a
slightly smaller one; oil drops usu-
ally conspicuous; solitary cells often showing a gliding or jerky
movement. DIATOMS. Fig. 243 1 /2 450

Figure 243%

345b Cells without silicious walls, so decorated; oil droplets lacking or
inconspicuous, not showing gliding movements; if motile, equipped
with flagella or moving by pseudopodia (amaeboid fashion) . . 346

346a Unicellular, with flagella but usually not swimming 347

346b Multicellular or colonial; motile or non-motile 365

145

HOW TO KNOW THE FRESH-WATER ALGAE

347a Cell within a variously shaped envelope (lorica), with a flagel-
lum opening 348

347b Cell without such an envelope.

352

348a Envelope cone-shaped, narrowed posteriorly to a blunt or sharp
point 349

348b Envelope flask-shaped, globose or pyramidal

350

349a Envelope with smooth or slightly wavy margins; without trans-
verse growth rings. See Fig. 243 D1NOBRYON

349b Envelope with marginal, bristle-like projections caused by trans-
verse growth rings. Fig. 244 HYALOBRYON

Fig. 244. Hyalobryon mucicola (Lemm.) Pascher.

This species is solitary and the envelope has margins
which have bristles which represent the remains of the
envelopes of previous generations of cells. Whereas
Dinobryon (Fig. 243) is freely swimming, this genus is
solitary or colonial as an epiphyte on filamentous algae.

Figure 244

350a (348) Cells free-swimming; envelope globose, with long spines;
flagellum collar narrow. Fig. 245 CHRYSOSTRELLA

Fig. 245. Chrysostiella paradoxa Chod.

This is the only species reported from this
country, occurring either in open water plank-
ton or intermingled among mixtures of algae
near shore. The test or envelope bears a
few long needle-like setae which are often
forked at the tips. The round or oval cells
with a short collar around the flagellum aper-
ture make this organism easy of identification.

Figure 245

350b Cells attached, usually not globose; without spines 351

146

HOW TO KNOW THE FRESH-WATER ALGAE

351a Envelope vase-shaped; transversely oval or pyramidal with base

next to the substrate. Fig. 246 LAGYNION

Fig. 246. a, Lagynion reductum

^=^

Presc; b, L. triangularis var.
pyramidatum Presc.

There are 3 or 4 species of this
genus which may be overlooked
in algal collections because they
are relatively small, often nearly
transparent, growing on the walls
of filamentous algae. The cells
are vase-shaped (triangular in op-
tical section), but this varies some-
what according to species. The protoplast contains a faintly pigmented,
yellowish chromatophore.

351b Envelope narrowed in the posterior portion. Fig. 247

Figure 246

DEREPYXIS

Figure 247

Fig. 247. Derepyxis dispar (Stokes) Senn.

The chief difference between this genus and
Lagynion (Fig. 246) is the presence of a sup-
porting membrane through the lorica upon
which the protoplast is suspended. This is the
only species reported from this country, occur-
ring as a minute epiphyte on filamentous
algae.

352a (347) Cells swimming by 1 flagellum; wall impregnated with vari-
ously shaped silicious scales (appearing like chain armor) which

bear bristles or needles. Fig. 248 MALLOMONAS

Fig. 248. a, Mallomonas

caudata Iwanoff; b, M.

pseudocoronata Presc;

c, M. acaroides Perty.

These species occur in

the open water plankton

of mostly hard water

lakes, frequently in abun-

Figure 248

dance. They are differ-
entiated one from the oth-
er by the shape and arrangement of the scales in the membrane and in
the arrangement of the bristles. They often occur in lakes in which
there is a high degree of pollution. Although motile, the single flagel-
lum is hardly distinguishable unless the cells are recently collected and
viewed under very favorable optical conditions.

147

HOW TO KNOW THE FRESH-WATER ALGAE

352b Cells either not motile, or moving by pseudopodia (amoeboid
fashion), or by 2 flagella; wall without scales and needles. . . .353

353a Cells amoeboid; protoplast very pale yellow-green or yellow-
brown 354

353b Cells swimming by 2 flagella, or sedentary; protoplast deeply
pigmented, usually a golden brown or blue 355

354a Pseudopodia long and needle-like. Fig. 249 RHIZOCHRYSIS

Fig. 249. Rhizochrysis limnetica
G. M. Smith, a, single cell; b,
/ cells in temporary colonial ar-

\\// \// / rangement.

• X. "^r^ This is the only species of the

~^\^v£tv . J^Cfer >)--. genus reported in the United

--^tf^sS if ^C^&i States. The amoeboid member of

-^/^-rASS^N^ \ the Chrysophyta has long, slen-

b \ der needle-like pseudopodia. Cells

are ordinarily solitary but may oc-

Figure 249 cur - m ] oosef temporarily united

colonies.

354b Pseudopodia short, tapering from the base to a fine point. Fig.
250 CHRYSAMOEBA

Fig. 250. Chrysamoeba radians
Klebs. a, single cell; b, tem-
porarily adjoined cells.

This species, the only one re-
ported, occurs more commonly
than Rhizochrysis (Fig. 249). Usu-
ally the cells occur in an amoe-
boid condition, bearing short,
sharply pointed pseudopodia, but
may change to a condition in
which a single flagellum is present
as a locomotory organ.

Figure 250

355a (353) Cells attached 356

355b Cells floating free, or swimming 357

148

HOW TO KNOW THE FRESH-WATER ALGAE

356a Cells inversely triangular, or tetrahedral in top view, angles tipped
with 1 or 2 spines. Fig. 251 TETRADIN1UM

Fig. 251. Tetradinium simplex Presc. a, side view;
b, vertical view.

The chromatophores of this sessile member of
the dinoflagellates are typically brown. The four
corners of the cell are tipped with 2 short spines.
This and 1 other species, T. javanicum Klebs, have
been reported as epiphytes on filamentous algae. It
should be compared with flaciborsJcia (Fig. 252) in
making determinations.

Figure 251

356b Cells inversely triangular, elliptic in top view, the outer free angles
tipped with 1 stout spine. Fig. 252 RACIBORSKIA

Fig. 252. Raciborskia bicornis Wo-
losz. a, side view, showing
stipe; b, top and lateral view.

These are elliptical cells, sessile
on a short stalk and attached to
filamentous algae or aquatic moss-
es. There is a single spine at each
pole of the cell. One species only
has been reported from the United
States. Compare with Tetradinium
(Fig. 252) in making determina-
tions.

Figure 252

357a (355) Cells crescent-shaped, the horns extended to form a spine-
like tip which is recurved in most species. Fig. 253

CYSTODINIUM

Fig. 253. Cystodinium corniiax (Schiller)
Klebs.

This and 2 or 3 other species occur
as free-floating members of the encys-
ted type of dinoflagellates. They are
differentiated on the basis of variations
of the crescent-shaped cells, with the
horns twisted at various angles. Sev-
eral species of Tetiaedron (Fig. 131) have been incorrectly described
from members of this genus.

Figure 253

149

HOW TO KNOW THE FRESH-WATER ALGAE
357b Cells not crescent-shaped 358

358a Cells broadly oval, ovate, or obovate, with a truncate or bilobed
anterior end; flagella 2, attached at the anterior end; chromato-
phores 2, lateral elongate plates 359

358b Cells shaped otherwise; flagella not anterior

360

359a Cells without a gullet in the anterior end, but with a slight apical
depression. Fig. 254 CHROOMONAS

Fig. 254. Chroomonas Nordstedtii Hansg.

These minute, slipper-shaped organ-
isms have 2 parietal, blue chromato-
phores, and 2 flagella that are attached
just below the apex of the cell. They
move rapidly and determinations can-
not be made unless some medium is
introduced to the mount to slow down
their action. Use 5% glycerin.

Figure 254

359b Cells with a gullet.

Figure 255

Fig. 255 CRYPTOMONAS

Fig. 255. Cryptomonas erosa Ehr.

There are probably several species of
this genus, but few are reported prob-
ably because they are easily overlooked
among dense mixtures of algae where
they mostly occur. The cells are rela-
tively larger than Chroomonas (Fig. 254)
and have a gullet at the anterior end

which can be seen as the cells rotate on their axis.

150

HOW TO KNOW THE FRESH-WATER ALGAE

360a (358) Cells with a long anterior horn and 2 or 3 posterior horns.
Fig. 256 CERATIUM

Figure 256

Fig. 256. Ceratium hirundinella (O. F. M.) Duj.

This distinctive organism is unmistakably identified. It occurs either
intermingled with other algae or in the open water of lakes where, un-
der favorable conditions, it may produce a veritable bloom and may
cause the water to be a gray-brown or coffee color. When recently
collected, favorable optical conditions will show the trailing flagellum
and the one that encircles the cell in the transverse groove. Most spe-
cies of this genus occur in the sea.

360b Cells without prominent horns as above

361

361a Cells without a true wall; membrane delicate, not showing a
pattern of plates; with a transverse groove which completely en-
circles the cell. Fig. 257 GYMNODINIUM

Fig. 257. a, Gymnodinium palustie Schil-
ling; b, G. fuscum (Ehr.) Stein.

Species of this genus are of wide
occurrence but seldom occur in large
numbers. They are intermingled among
other algae and are usually found very
at^ ] actively swimming in microscope
mounts. The thin cell membrane (with-
out a cell wall) that characterizes most
fresh<water species helps in identifica-
tion. The transverse furrow extends
around the cell in a downward spiral
fashion.

Figure 257

361b Cells with a definite wall; a pattern of definitely arranged plates
usually evident; a transverse groove encircling the cell, complete-
ly or incompletely 362

151

HOW TO KNOW THE FRESH-WATER ALGAE

362a Wall thick; plates easily seen, with a suture between the plates

usually evident; transverse furrow completely encircling the cell.

363

362b Wall thin; plates seen with difficulty (especially in filled and liv-
ing cells); transverse furrow completely encircling the cell or not.
364

363a Wall with 2 antapical plates (plates at the posterior pole, to be
seen in end view of the cell); cell slightly flattened dorsiventrally
in most species. Fig. 258 PERIDINIUM

Figure 258 Vi
Figure 258 "

Fig. 258. Peridinium wisconsinense Eddy, a, ventral view showing
longitudinal sulcus; b, dorsal view; c, posterior polar view showing
2 antapical plates.

Fig. 258 Vi. Encysted Dinoflagellates.

This genus is represented by more species in fresh water than any
of the other dinoflagellates. They are differentiated by shape, size and
details of plate number and arrangement. The 2 posterior or antapical
plates can be determined by patiently rolling the cell so that it can
be seen from the bottom. Although very common, these species do not
form blooms nor pure growths as does Ceratium (Fig. 256).

363b Wall with 1 antapical plate; cell not flattened dorsiventrally (round
in cross section). Fig. 259 GONYAULAX

Fig. 259. Gonyaulax palustre Lemm.

These almost spherical cells are differentiated
from Peridinium (Fig. 258) by the presence of but a
single antapical plate and the slightly spiralled
transverse furrow. Some authorities regard this
particular species of the genus as belonging to
Peridinium.

Figure 259

152

HOW TO KNOW THE FRESH-WATER ALGAE

364a (362) Cells strongly ilattened dorsiventrally; plates not evident;

transverse furrow not completely encircling the cell. Fig. 260 ....

HEMIDIN1UM

Fig. 260. Hemidinium nasutum Stein, a, ven-
tral view; b, dorsal view.

There are several species of this genus re-
ported from the United States. They are dif-
ferentiated by shape and size of cell and by
the pattern of the plates which are usually
very delicate and difficult of determination.
The cells are very much flattened when seen
from the side.

Figure 260

364b Cells not at all or but very little flattened dorsiventrally (nearly
round in cross section); plates evident (especially in empty cells);

transverse furrow completely encircling the cell. Fig. 261

GLENODINIUM

Fig. 261. Glenodinium Kulczynski (Wolos.)
Schiller, a, ventral view showing longitudi-
nal furrow; b, dorsal view; c, apical view.

The several species of this genus reported
from the United States are differentiated by
cell size and shape. The plate pattern is
much more easily discerned than in Hemidini-
um (Fig. 260) but patience is required in rotat-
ing the cell in order to determine this pattern.
As in other genera, especially Peridinium (Fig.
258) it is desirable to examine empty cells in
order to see the wall characters plainly. Most
species are globular or if flattened, not so
much as in Hemidinium.

Figure 261

365a (346) Colony mottle by flagella 366

365b Colony non-motile, or if moving, by rhizopodial processes (pseudo-
podia) 370

366a Colony globose or subglobose (oval); cells ovoid or pear-shaped,
compactly arranged or forming a hollow sphere 367

366b Colony not globular; cells shaped otherwise 369

153

HOW TO KNOW THE FRESH-WATER ALGAE

367a Cells bearing 2 long, rigid, rod-like processes at the anterior end.
Fig. 262 CHRYSOSPHAERELLA

Fig. 262. Chrysosphaerella longispina
Lauterb.

This distinctive organism is easily-
identified by the curious long rods,
borne in pairs on each cell. The
chromatophores are brownish-yellow.
Although widely distributed the species
(only 1 reported) seems to be rather
rare in occurrence.

Figure 262

367b Cells without such rods

368

368a Cells elongate-ellipsoid or elongate pear-shaped, rather compact-
ly arranged in the colony; cell wall with minute silicious scales in
the anterior end; flagella 2, of equal length. Fig. 263 .... SYNURA

Fig. 263. Synura uvella Ehr. a, colony;
b, single cell showing silicious spi-
cules in membrane.

This species is very common in hard
water lakes and may be so abundant
as to produce disagreeable odors and
tastes in water supply reservoirs. The
chromatophores are golden brown and
mask the small spicules in the walls at
the anterior end of the cell. These can
be determined by proper focusing on
colonies that are quiescent. There is
another species with longer and nar-
rower cells, S. Adamsii G. M. Smith, that
is of more rare occurrence.

Figure 263

154

HOW TO KNOW THE FRESH-WATER ALGAE

368b Cells ovoid or pear-shaped, separated and evenly spaced within
the colonial envelope; without scales in the wall; flagella 2, of
unequal length. Fig. 264 UROGLENOPS1S

Fig. 264. Uioglenopsis ameiicana (Cal-
kins) Lemm.

J^£S^ ^ 0,(3 .0 d A fi^

^

.-y^^V? b ~& ft

iss ^ <? * ® ®

or

a. q*-

'-« -©

*K«*f

This species frequents bodies of water
^c^Jff that are contaminated with sewage and
organic wastes. The colonies are large
and contain several hundreds of cells,
are sometimes mistaken for Volvox (Fig.
15) but is quickly differentiated by the
&\»*5? yellow-brown color of the plate-like (not

cup-shaped) chromatophores.

m

Figure 264

369a (366) Cells elongate-ovoid or pear-shaped, compactly arranged
side by side in radiate fashion in 1 plane to form a plate with a
small opening in the center of the colony; motile by 2 flagella.
Fig. 265 CYCLONEXIS

Fig. 265. Cyclonexis annularis Stokes. (Re-
drawn from Stokes).

The flat, disc-like colony of compactly ar-
ranged, pear-shaped cells is very distinctive.
The flagella are relatively coarse and can
be seen easily when the colony is quiescent.
There are 2 elongate, lightly pigmented chro-
matophores.

Figure 265

369b Cells not as above; contained in a vase-shaped envelope, 1 or 2
such envelopes arising from the mouth of the one below to form
a branched series. See Fig. 243 DINOBRYON

370a (365) Individuals furnished with pseudopodia (colony sometimes
loosely formed and only temporary) 37 1

370b Individuals not furnished with organs of locomotion; colonies
non-motile 373

155

HOW TO KNOW THE FRESH-WATER ALGAE

371a Cells joined together by long, narrow protoplasmic extensions,
arranged in a linear series. Fig. 266 CHRYS1DIASTRUM

Fig. 266. Chrysidiastrum catenation Lau-
ter. (Redrawn from Smith).

Although this organism may occur

singly it is- frequently seen adjoined

in loose colonies by the interconnecting

pseudopodia. There is 1, plate-like or

Figure 266 disc-shaped chromatophore.

371b Cells not joined as above

372

372a Pseudopodia numerous, radiating needles; colony formation most-
ly temporary and incidental. See Fig. 249 RH1ZOCHRYSIS

372b Pseudopodia short protoplasmic extensions which join individuals
to form temporary colonies. See Fig. 250 CHRYSAMOEBA

373a (370) Colony consisting of vase-shaped envelopes, 1 or 2 such
envelopes arising from the mouth of one below to form forked
series (organisms actually motile by flagella, but often appear-
ing quiescent with flagella completely invisible in microscope
mounts). See Fig. 243 DINOBRYON

373b Individuals not cone-shaped; colony formed otherwise 374

374a Thallus a sparsely branched gelatinous cylinder or a mucilaginous
network, with cells arranged in 1 to several irregular linear series.
Fig. 267 PHAEOSPHAERA

Fig. 267. Phaeosphaera perforata Whitford. a,
small portion of perforate colony; b, cells
showing chromatophores.

The golden brown cells of this species occur
in gelatinous masses of irregular shape and of
macroscopic size. The thallus may be a stringy
mass of mucilage occurring in skeins or mesh-
works. Unlike Tetraspora (Fig. 35) with which
it might be mistaken, the cells are not arranged
in groups of 4 but occur in irregular series
throughout the gelatinous strands.

Figure 267

374b Thallus not a branched gelatinous strand or network 375

156

HOW TO KNOW THE FRESH-WATER ALGAE

375a Cells in clusters of 2-4-8-16 within an irregularly globose colonial
investment. Fig. 268 CHRYSOCAPSA

Fig. 268. Chrysocapsa planctonica (West
& West) Pascher. (Redrawn from
Smith).

The colonies of this species are globu-
/ lar, or nearly so, the mucilage clear
and transparent, the cells with brown-
ish chromatophores. This is the only
species reported which is common, but
another one, C. paludosa (West & West)
Pascher, with oval cells has been re-
corded.

Figure 268

375b Cells 16-32-64 within a wide, flat colonial mucilage, the cells radi-
ally arranged in 1 plane; colonial mucilage impregnated with
granular substance. Fig. 269 CHRYSOSTEPHANOSPHAERA

Fig. 269. Chrysostephanosphaera globu-
litera Scherff.

Figure 259

This colony of brown cells is disc-
like and is enclosed by a wide gelatin-
ous matrix which invariably contains
dark granules of what is regarded as
metabolic waste products. Only 1 spe-
cies is known from this country.

376a (4) Plants filamentous, thread-like (the thread of cells called a
trichome; trichome and sheath, if present, called a filament). . .377

376b Plants not definitely filamentous; cells globular, rod-shaped, or
angular from mutual compression; solitary, in floating colonies, or
forming cushion-like masses in which a suggestion of filamentous
arrangement may be apparent 421

377a Trichome coiled or spiralled in a regular fashion 378

377b Trichomes otherwise, straight or irregularly twisted (occasionally,
however, Oscillatoria (Fig. 277) may become twisted about itself
to form a regular spiral) 381

157

HOW TO KNOW THE FRESH-WATER ALGAE

378a Trichome unicellular. Fig. 270 SPIRULINA

Figure 270

Fig. 270. a, Spirulina laxissima G. S. West; b, S. princeps (West &
West) G. S. West; c, S. subsalsa Oersted.

Although essentially unicellular, this genus is thread-like and is
included with the Oscillatoriaceae (a filamentous family of the Cyano-
phyta). Although some species are solitary they are often found in
masses either by themselves or intermingled with Oscillatoria (Fig.
277). Species are differentiated by size and by type of coiling of the
cell. They are usually actively in motion when viewed microscopically.
Movement in this and other blue-green genera is accomplished by the
extrusion of mucilage.

378b Trichomes multicellular, i.e., with cross walls 379

379a Trichomes composed of bead-like or barrel-shaped cells, with heter-
ocysts present (cells located here and there in the trichome which
are larger and sometimes different in shape from the vegetative
colls). Fig. 271 ANABAENA

Fig. 271. a, Anabaena spiroides
var. crassa Lemm.; b, A. sub-
cylindrica Borge, showing
spores; c, A. sp., showing oval
akinete; d, A. subcylindrica
Borge, showing heterocysts.

There are many species of this
genus, some solitary and some
forming colonial masses of indefi-
nite shape. When colonial they
are surrounded by a conspicuous
mucilage and sometimes are mis-
taken for Nostoc (Fig. 300). The
colonial mass is indefinite in shape
and the mucilage soft, however.

Whereas some forms are truly
planktonic species, others occur intermingled with algae in shallow
water or on moist soil. The planktonic species may form a bloom in
lakes of northern latitudes during summer months, but seldom cause
disagreeable conditions in lakes or reservoirs because the plants re-
main suspended throughout the water and do not form surface scums.
Anabaena spp. are responsible for the death of cattle and other animals
drinking from infested water.

Figure 271

158

HOW TO KNOW THE FRESH-WATER ALGAE

379b Cells not bead-like; heterocysts absent

380

380a Trichomes with a sheath. Fig. 272 LYNGBYA

Fig. 272. a, Lyngbya contorta
Lemm; b, L. Birgei G. M. Smith.

Most species are straight and
rigid, but a few are coiled; some
are planktonic. The definite, rath-
er firm sheath ex*ending beyond
the end of the trichome (the row
of cells) is characteristic and
helps to separate this genus from
Oscillatoria (Fig. 277). One species, L. Birgei, is so characteristically
a planktonic species in hard water that it can be used as an index
organism.

;W^i e H

;£:-;:H : ;

? v oK

m

w.:

H^m

S P

Figure 272

380b Trichomes without a sheath. Fig. 273 ARTHROSPIRA

Figure 273

Fig. 273. Arthiospiia Jenneri (Kuetz.) Stiz.

The plants in this genus are multicellular but at times the cross
partitions are difficult to discern and short sections may be mistaken
for Spirulina (Fig. 270). Species are differentiated mostly by size and
form of coiling of the filaments; occur on damp soil of beaches, or in
the tychoplankton.

381a (377) Trichomes with cells all alike in shape and size (except
trichome) may be tapered, or the apical cell capitate (swollen) . 382

381b Trichomes with certain cells enlarged and appearing empty or
with homogeneous contents (heterocysts); in some, certain cells
become enlarged and develop thick walls, forming spores (aki-
netes) 397

382a Trichomes tapering from base to apex 383

382b Trichomes not tapering from base to apex, the same diameter
throughout, or tapered only in the extreme apical region 385

159

HOW TO KNOW THE FRESH-WATER ALGAE

383a Trichomes aggregated, tapering from a base which is incorporated
in a prostrate cushion of cells. Fig. 274 AMPHITHR1X

Fig. 274. Amphithiix jan-
thina (Mont.) Bor. & Flah.
(Redrawn from Bornet &
Flahault).

Figure 274

These tapering filaments
are arranged in somewhat
parallel fashion to form clusters (but without conspicuous mucilage) at-
tached to substrates. There is a weakly developed, prostrate expan-
sion of the thallus from which the filaments arise. The lack of hetero-
cysts (see Anabaena, Fig. 271) makes this a somewhat anomalous mem-
ber of the Rivulariaceae which characteristically has this type of cell
at the base of the filament.

383b Without a prostrate cushion of cells at the base of the trichome.
384

384a Trichomes gregarious, parallel in a colonial mass. See Fig. 274.
AMPHITHRIX

384b Trichomes solitary or loosely clustered, not parallel. Fig. 275 . . .
CALOTHR1X

Fig. 275. a, Calothrix epiphytica West
& West; b, C. atricha Fremy; c,
C. Braunii Bor. & Flah.

These tapering filaments are soli-
tary or loosely clustered, although
sometimes gregarious, forming ex-
tensive masses. There is a basal
heterocyst and in some species,
akinetes. Species are differentiated
on the basis of size, presence or
absence of akinetes, and by the
degree of tapering of the trichome,
some being very abrupt.

160

HOW TO KNOW THE FRESH-WATER ALGAE

385a (382) Filaments bearing false branches (a branch formed by pro-
liferation of a broken trichome which pushes off to one side of the
main axis; not branching by lateral division of a cell in the main
axis); branching often sparse. Fig. 276 PLECTONEMA

Fig. 276. Plectonema Wollei
Farlow.

The false habit of branching

places this genus in the Scy-

tonemataceae, but unlike other

Figure 276 members of the family there

are no heterocysts. The spe-
cies illustrated is a common one, occurring in brownish green or black,
cottony masses at or near the surface of the water; is a relatively large
species being up to 50 /x in diameter.

385b Filaments not branched 386

386a Trichomes without a sheath 387

386b Trichomes with a sheath 388

387a Trichomes solitary or intermingled, not lying in parallel bundles,
sometimes tapered slightly at the anterior end, or with the apical
cell swollen (capitate). Fig. 277 OSCILLATOR1A

Figure 277

Fig. 277. a, Oscillatoria rubescens DeCand.; b, O. splendida Grev.

The chief characteristic of species in this genus is their lack of a
sheath and another one is their active, oscillating movement. A mass
of the plants left in a laboratory dish will creep up the sides of the con-
tainer. There are numerous species, differentiated on the basis of size
and cell proportions and also upon the morphology of the apex of the
trichome, sometimes being straight and not tapering, sometimes taper-
ing and possessing a swollen apical cell.

161

HOW TO KNOW THE FRESH-WATER ALGAE

387b Trichomes lying in parallel bundles, not tapered at the anterior
end; apical cell never capitate. Fig. 278 TR1CHODESMIUM

Fig. 278.
Kleb.

Trichodesmium lacustre

Figure 278

This is a species of uncertain
position because it has an Anaba-
ena - like filament, but without
heterocysts. The filaments are ar-
ranged in parallel bundles which form free-floating, dark-green flakes.
The cells contain numerous pseudovacuoles (gas pockets). T. erythra-
ceum Ehr. is a marine species which, because of light refraction from
pseudovacuoles, produces a color that gives the Red Sea its name.

388a (386) Sheath containing one trichome

389

388b Sheath containing more than one trichome

394

J89a Sheath firm and definite, not adhering to sheaths of adjacent fila-
ments 390

389b Sheath soft and sticky, often adhering to sheaths of adjacent
plants and intermingling (confluent) with them 391

390a Sheaths purple or reddish, conspicuously stratified. Fig. 279 ....
PORPHYROSIPHON

Fig. 279. Porphyrosiphon Notarisii

(Menegh.) Kuetz.

The purple color of the lamellated
sheath of this species accounts for
the brightly colored patches on damp
soil in subtropical sections of the
country. There is but 1 species re-
corded for the United States.

m

f*T

urn

Figure 279

390b Sheaths colorless or yellowish, not stratified, or indistinctly so.
See Fig. 272 LYNGBYA

162

HOW TO KNOW THE FRESH-WATER ALGAE

391a (389) Filaments forming an expanded plant mass with or without
erect tufts » • • 392

391b Filaments not forming an expanded mass or stratum 393

392a Plant mass having erect tufts. Fig. 280 SYMPLOCA

Fig. 280. Symploca mus-
corum (Ag.) Gom.

Filaments of this spe-
cies occur in erect tufts in
Figure 280 moist aerial situations.

Species which have thin,
sticky sheaths should be compared with Phormidium (Fig. 281) with
which they may be confused if seen individually and not in colonial
mass.

392b Plant mass without erect tufts.
Fig. 281 PHORMIDIUM

Figure 281

Fig. 281. a, Phormidium ambiguum Gom.; b, P. favosum (Bory) Gom.;
c, P. inundafum Kuetz.

There are numerous species of this genus, differentiated by size
and by characteristics of the apical cell of the trichome. The
sheaths are thin and sticky, hence the plants form rather closely com-
pacted mats that coat over submerged surfaces. Such a mat when
handled does not break apart easily (as somewhat similar-appearing
growths of Oscillatoiia, Fig. 277, might do). The plant masses are
blue- or black-green in color and feel slimy or slippery to the touch.

393a (391) Filaments lying parallel in free-floating bundles. See Fig.
278 TRICHODESMIUM

163

HOW TO KNOW THE FRESH-WATER ALGAE

393b Filaments irregularly intermingled, not arranged in free-floating
bundles. Fig. 28P/2 PHORMID1UM

Figure 281Vi

Fig. 281 ¥t. Phormidium sp. Isolated filament.

394a (388) Sheaths soft and sticky, without an even, definite outer boun
dary

395

394b Sheaths firm and definite, not mucilaginous 396

395a Sheaths containing 2 or 3 trichomes. Fig. 282. . . HYDROCOLEUM

Fig. 282. Hydrocoieum oligoiri-

chum A. Braun.

In this genus there are only 3
(sometimes 4) trichomes within a
wide, lamellate, gelatinous sheath.
Figure 282 The filaments may be solitary or

spread in a thin layer on damp soil. H. oJigofrichum usually is lime-
encrusted, whereas H. homeotrichum Kuetz. is not.

395b Sheaths containing many trichomes. Fig. 283 M1CROCOLEUS

Fig. 283. a, Microcoieus vagi-
natus (Vauch.) Gom.; b, M.
lacustris (Rab.) Farlow.

There are several species of
this genus, differentiated by
size and character of the apical
cell. Unlike Hydrocoieum (Fig.
282) there are many intertwined
trichomes in each sheath. Usu-
ally the trichomes show an ac-
tive slithering motion over one another, may emerge from the end of
the sheath and then retract. The thallus is often of macroscopic size
as it grows on damp soil. Some species are more often found on
submerged substrates, however.

Figure 283

164

HOW TO KNOW THE FRESH-WATER ALGAE

396a (394) Sheaths wide, containing 2 or 3 loosely arranged trichomes.
Fig. 284 DASYGLOEA

Fig. 284. Dasygloea sp.

The sheaths of the plants in this
genus are rather firm and definite
in outline, contain but 1 to 3 tri-
chomes. See D. amorpha Berk. The
sheaths are usually forked or
branched at the ends (as they are
also in Schizothrix, Fig. 285, with
Only one species is reported from

Figure 284

which it should be compared)
the United States.

396b Sheaths close, usually containing several crowded trichomes. Fig.
285 SCHIZOTHRIX

Figure 285

Fig. 285. Schizothrix tinctoiia Gom.

In this genus theie are but few trichomes within a definite and
rather firm sheath. The plant masses are of macroscopic size and
often form streaming masses, or films and wefts over submerged
vegetation. Several of the species quickly disintegrate when stored in
a covered container for a short time without preservative and liberate
a copious amount of the phycocyanin pigment which is present in
blue-green algae. There are at least a dozen species reported from
the United States, differentiated by size and cell proportions.

397a (381) Trichomes tapering from base to apex 398

397b Trichomes not tapering from base to apex 402

398a Filaments inclosed within abundant mucilage, forming a globular
or hemispherical body, attached or free-floating 399

398b Filaments not inclosed by abundant mucilage to form a thallus
of definite shape , 401

165

HOW TO KNOW THE FRESH-WATER ALGAE

Figure 286

399a Sheath containing 2 or more trichomes. Fig. 286. . .SACCONEMA

Fig. 286. Sacconema rupes-
tre Borzi. a, habit of col-
ony; b, filaments from col-
ony.

Trichomes in this genus
are tapering from a basal
heterocyst as in Gloeotrichia
(Fig. 287) but there is more
than 1 trichome within a
sheath and the gelatinous
colony is very irregular in
shape as it occurs on stones
(sometimes in very deep water). The sheaths are wide, lamellate and
are flaring at the outer end.

399b Sheath containing 1 trichome 400

400a With cylindrical spores adjoining a basal heterocyst; colonial
mucilage soft in floating species, firm when attached to substrates
and then forming hemispherical growth 1-3 mm. in diameter.
Fig. 287 GLOEOTRICHIA

Fig. 287. a, Gloeothrichia Pisum (Ag.) Thur.,
habit on Ceratophyllum; b, diagram of fila-
ment arrangement; c, G. echinulata (J. E.
Smith) P. Richter, diagram of filaments in
colony; d, diagram of base of single fila-
ment showing heterocyst and spore.
In this genus the tapering trichomes are
encased in mucilage which is usually soft (al-
though firm in 1 species) and they are not so
closely compacted as in Rivularia (Fig. 288),
a genus which is very similar. Gloeotrichia
produces filaments with large akinetes
(spores) adjoining the basal heterocyst when
mature. One of the most common species
is the free-floating G. echinulata which occurs
in abundance in some lakes and gives the
appearance of the water being filled with
tiny tapioca-like grains, buff-colored. G. na-
tans (Hedw.) Rab. is also fairly common. It begins as an attached
plant but late in the growing season it appears at the surface in brown
gelatinous masses, either expanded and flat or irregularly globular.
G. Pisum forms hard, green or black balls, 1 or 2 mm. in diameter on
submerged vegetation, sometimes completely covering the host plant.
When plants in this genus are young the spores will not be present, in
which case they may be confused with Rivularia (Fig. 288) which never
produces spores, has a much harder colonial mucilage and has tri-
chomes more densely packed, often parallel in arrangement.

Figure 287

166

HOW TO KNOW THE FRESH-WATER ALGAE

400b Spores absent; trichomes embedded in hard mucilage to form
globular thalli which may coalesce, thus producing a continuous
stratum; trichomes parallel and densely compacted or radiate.
Fig. 288 RIVULARIA

Fig. 288. Rivularia sp. a, diagram of
portion of attached colony to show
arrangement of filaments; b, one fila-
ment showing basal heterocyst.

There are several species of this
genus reported from the United States.
They may be differentiated from Gioeo-
trichia by the hardness of the mucilage,
the compactness of arrangement of the
trichomes, and the absence of akinetes.
Small globular balls or expanded mass-
es of dark green mucilage occur on
rocks or submerged logs, etc. Some
species grow in moist aerial surfaces,
especially marine forms. Rivularia is
not found free-floating, whereas Gioeo-
See notes under the latter genus.

Figure 288

trichia (Fig. 287) usually is.

401a (398) Filaments branching freely; the basal portion of the branches
lying within the sheath of the main filament for some distance,
then diverging. Fig. 289 DICHOTHR1X

Fig. 289. Dichothrix gypsophila
(Kuetz.) Bor. & Flah.

In this genus the tapering tri-
chomes are enclosed 2 or 3 to-
gether within branching sheaths.
Brush-like tufts are produced by
their habit of growth and these
sometimes attain macroscopic pro-
portions. The species are differ-
entiated by size and sheath char-
acters. They are customarily

found intermingled with miscellaneous algae; are sometimes attached

or at least adherent to aquatic plants.

Figure 289

401b Filaments not branched (or seldom so); if branched, the branches

not inclosed in the sheath of the main filament. See Fig. 275.

CALOTHRIX

167

HOW TO KNOW THE FRESH-WATER ALGAE

402a (397) Trichomes branching by lateral division of cells of the main

axis (true branching) 403

402b Tichomes unbranched, or with false branches (sections of tri-
chome developing a series of cells to one side of a break in the

main axis) 406

403a Individual trichome sheath not apparent; colony of trichomes in-
vested by a mucilage; heterocysts usually on the ends of short

branches. Fig. 290 . NOSTOCHOPSIS

Fig. 290. Nostochopsis lobatus
Wood, a, diagram of filament
arrangement in colony; b-d, fila-
ments and lateral heterocysts.

This is the only species reported
from the United States. The fila-
ments are composed of Anabaena-
like cells and bear true branches.
The heterocysts are borne lateral-
ly along the filaments or on the
ends of short branches (rarely in-
tercalary also). The filaments are
colonial and are inclosed in a firm
mucilage in the form of cylinders
or hollow tubes which extend ver-
tically from the bottom in quiet
Figure 290 water, or lie horizontally in cur-

rents. In shallow water the gelatinous tubes may reach the surface
and then broaden and flatten horizontally.

403b Individual trichome sheaths evident; heterocysts in the same ser-
ies with the main axis, or cut off laterally from them but not on

the ends of branches 404

404a Filaments closely aggregated, forming an attached, gelatinous
thallus 1-2 mm. in diameter. Fig. 291 CAPSOSIRA

Fig. 291. Capsosira Brebissonii Kuetz. a, habit of at-
tached colony; b, portion of filament showing lat-
eral heterocysts. The sheath is thin and soft with-
out a definite limiting membrane.

This species builds small bulbous mucilaginous
colonies attached to the substrate. The individual
trichomes which bear true branches are surrounded
by a definite sheath which' is yellowish. Heterocysts
are usually lateral, but may be intercalary in the
trichomes which do not taper toward the apices. There
is but 1 species reported from widely separated sta-
tions in the United States.

168

HOW TO KNOW THE FRESH-WATER ALGAE

404b Filaments not forming a definitely shaped gelatinous thallus, but
spreading irregularly 405

405a Filaments with more than 1 series of cells within a wide gelatinous
sheath; heterocysts small, cut off laterally from the vegetative
cells. Fig. 292 ST1GONEMA

Fig. 292. a. Stigonema muscicola Borzi
(Fischerella muscicola (Thur.) Gom.); b,
S. turfaceum (Berk.) Cook.

Although there are several species re-
ported from the United States, S. furfaceum,
and S. oceliafum (Dillw.) Thur. are by
far the most common. The latter is one
which frequently does not show the mul-
tiseriate arrangement of cells. The sheath
is wide and mucilaginous and in some
species is distinctly lamellate. The hetero-
cyst typically is cut off laterally from a
vegetative cell. S. ocellatum shows inter-
cellular connections. These species form
brownish or blue-green growths on submerged reed stems, on exposed
roots, and on other aquatic vegetation, or they may occur as velvety
growths on moist soil, rocks, or concrete. Stigonema ocellatum invari-
ably is found in acid water (desmid) habitats.

Figure 292

405b Filaments with cells in 1 series within a narrow sheath; hetero-
cysts within the series of vegetative cells (intercalary). Fig. 293.
HAPALOSIPHON

Fig. 293. Hapalosiphon hibernicus West &
West.

This genus is differentiated from Stigo-
nema (Fig. 292) principally by the fact that
the cells are always arranged in a single
series with the heterocyst (usually some-
what rectangular) intercalary rather than
lateral. Species are differentiated mostly
by size and by habit of growth, some
sprawling irregularly over a substrate, oth-
ers branching more regularly and erect.
Whereas Sfigonema cells are usually
rounded or oval and sometimes show in-
tercellular connections, those of Hapalosi-
phon are ordinarily quadrate or quadran-

gular-globcse and more compactly arranged within a close, thinner

sheath.

Figure 293

169

HOW TO KNOW THE FRESH-WATER ALGAE
406a (402) Trichomes unbranched 407

406b Trichomes with false branches 417

407a Individual trichome sheath firm and definite; heterocyst basal
(rarely intercalary heterocysts also). Fig. 294. . . MICROCHAETE

Fig. 294. a, Microchaete diplosi-
phon Gom.; b, M. iobusta Setch.
& Gard.

Plants of this genus are mostly
epiphytic, with part of the fila-
ment lying parallel with the sub-
strate and then curving away. The
filaments do not taper (or scarcely
so) and although there may be in-
tercalary heterocysts they usually
are basal. There are 4 species
described from the United States.

Figure 294

407b Individual sheath soft, often indistinct and intermingled with co-
lonial mucilage; heterocysts either all terminal or all intercal-
ary 408

408a Heterocysts terminal 409

408b Heterocysts intercalary 410

409a Spores adjacent to the heterocysts which usually are at one end of

the trichome. Fig. 295 CYL1NDROSPERMUM

Fig. 295. a, Cylindrospermum majus
arxzC I OCCoqd Kuetz.; b, C. marchicum Lemm.

^rxc" CS3^^ ^^b The chief characteristic of this genus
cxDoooa30oooooou^ r ^v ) is the location of the heterocysts and

-BBgr,. ? spores, always terminal and usually

^■•k>*" only at one end of the trichome which
Figure 295 does not taper at the extremeties. The

plants form gregarious patches or films
over submerged vegetation. The spores are formed singly or in series
just back of the heterocyst. Frequently a dense 'nest' of spores will
be found left where there has been a colony of filaments. Some spe-
cies are terrestrial.

170

HOW TO KNOW THE FRESH-WATER ALGAE

409b Spores not adjacent to the heterocysts; heterocysts at both ends
of the trichome. Fig. 296 ANABAENOPSIS

Fig. 296. Anabaenopsis Elenkinii Miller.
(Redrawn from Smith).

There are 3 species of this genus re-
ported from the plankton in the United
States. The trichomes are usually rela-
tively short and are coiled.

Figure 296

410a (408) Thallus composed of many trichomes; usually parallel with-
in colonial mucilage 411

410b Plant a solitary trichome, or if aggregated, not parallel, but en-
tangled within colonial mucilage 413

411a Trichomes inclosed in abundant mucilage; arranged to form a
hollow, attached tubular thallus. Fig. 297 WOLLEA

Fig. 297. Wollea saccata (Wolle) Born. & Flah. a, habit
of colony; b, trichomes in detail showing heterocysts,
and akinetes in a series.

The filaments of this species He more or less parallel
in long, gelatinous, tube-like or sac-like thalli which grow
vertically from the bottom in standing water. The cells
are barrel-shaped or Anabaena-like, and the intercalary
heterocysts are cylindrical or nearly so.

Figure 297

411b Thallus not a gelatinous tube 412

171

gPZLI 1 ucr

dcz i i i i i i 1 1 i i i nanxi

Figure 298

HOW TO KNOW THE FRESH-WATER ALGAE

412a Trichomes parallel, forming a free-floating flake or bundle, con-
taining a single heterocyst and a spore near the middle of each
trichome. Fig. 298 APHAN1ZOMENON

Fig. 298. Aphanizomenon
fios-aquae (L.) Ralfs. a,
diagram of colony; b,
a few trichomes from
the colony; c-d, tri-
chomes in detail show-
ing medially located
cylindrical akinete.

This is the only com-
mon species reported
from this country and is
very widely distributed in lakes which are rich in nitrogen and phos-
phorus. The trichomes He in parallel bundles and form flakes of
macroscopic size. Because of the gas vacuoles (pseudovacuoles) the
plants float high in the water and form surface scums and mats.
Hence they are able to cause serious trouble in lakes and reservoirs
used for water supplies and pleasure resorts. During summer months
the species may develop a "bloom" condition and be so abundant as
to give the water the appearance of "pea soup." Considerable eco-
nomic loss is suffered as a result of the disturbance caused by Aphani-
zomenon when it leads to the death of fish. It is a plant that usually
accompanies human settlement about lakes and rarely is the plant
found in abundance in lakes remote from habitation.

412b Trichomes not parallel, or if so, forming indefinitely shaped flakes.
See Fig. 271 (in part) ANABAENA

413a (410) Trichomes planktonic, solitary 414

413b Trichomes colonial, in a gelatinous mass 415

414a Vegetative cells and heterocysts disc-shaped, wider than long.
Fig. 299 NODULARIA

IBHI

c^^ SrooQJMxPGairo ^c^;

Fig. 299.

Figure 299

Nodularia spumigena Mert.

Filaments of this species are at once distinguishable by the very
short, compressed vegetative cells and heterocysts. The sheath is
rather thin and mucilaginous and sometimes is not immediately ap-
parent. The species illustrated is the most common of the 4 that are
reported from the United States. Plants of this genus are usually
found intermingled with miscellaneous algae from the tychoplankton.

172

HOW TO KNOW THE FRESH-WATER ALGAE

414b Cells globose to cylindric, or barrel-shaped, not compressed as
above. See Fig. 271 ANABAENA

415a (413) Plant mass definite in shape, usually globular, bound by a
firm, gelatinous tegument; colonies microscopic or macroscopic.
Fig. 300 NOSTOC

Fig. 300. a, Nostoc pruniforme Ag.,
showing habit of colonies; b, N.
linckia (Roth) Bor. & Flah., with
two trichomes in detail showing
heterocyst and akinetes.

Figure 300

This genus is characterized chiefly
by the firm outer tegument of the
mucilaginous material in which nu-
merous bead-like filaments are in-
closed, thus giving the thallus a defi-
nite form. One species forms colon-
ies as large as a goose egg, whereas another, N. commune Vauch.,
builds tough, membranous green or brown layers on the bottoms of
pools or in swampy places, sometimes in wet alpine meadows. N.
pruniforme is a very common species which forms marble- or acorn-
sized colonies on damp soil, often among grasses in marshy meadows.
The globular or oval thalli are frequently mistaken for turtle or some
other type of reptilian egg. N. amplissimum Gard. is known as Mare's
Eggs in the far West where it produces colonies 10 cm. in diameter.

415b Plant mass not definite in shape; mucilage soft, not bounded by
a firm tegument 416

416a Trichomes forming small bundles within a gelatinous sheath, eith-
er entangled or parallel. Fig. 301 AULOS1RA

Fig. 301. Aulosira laxa Kirch.

This species (the only one
of the genus found in the
United States) is much like
Microchaete (Fig. 294) and
the genus is sometimes clas-
sified with it. Some authori-
ties differentiate it on the
basis of the soft sheath, the intercalary heterocysts, and the akinetes
which occur intercalary and of the same size and proportions as the
heterocysts.

416b Trichomes not forming bundles. See Fig. 271 ANABAENA

Figure 301

173

HOW TO KNOW THE FRESH-WATER ALGAE

417a (406) Branches arising in pairs about midway between 2 hetero-
cysts (branching rarely solitary). Fig. 302 SCYTONEMA

Fig. 302. Scytonema Aichangelii
Born. & Flah.

There are several species of
this genus which are very com-
mon. Although some branch
rather seldom, most of them show
numerous false branches which
arise singly or in pairs between
the heterocysts. They are plants
of both aquatic and subaerial
habitats. Species are differenti-
ated by size, shape of cell, and
sheath characters.

Figure 302

417b Branches arising singly just below a heterocyst or a series of
them; (branching sometimes rare and not definite, requiring a
search through a number of plants to determine this character).
418

418a Sheath close and firm, 1 trichome in a sheath 419

418b Sheath usually wide and soft; at least more than 1 trichome with-
in a sheath 420

419a Branches frequent, arising just below the heterocysts which are
always intercalary. Fig. 303 TOLYPOTHRIX

Fig. 303. Tolypothrix distorta Kuetz.

This genus is differentiated from Scy-
tonema (Fig. 302) principally by the
fact that the false branch always arises
below a heterocyst or sometimes below
a series of them. There are several
species that are common, differentiated
by size and by sheath characters, some
of which are thick and lamellate, others
thin and soft.

Figure 303

419b Branches rare; heterocysts terminal (rarely intercalary also). See
Fig. 294 MICROCHAETE

174

HOW TO KNOW THE FRESH-WATER ALGAE

420a (418) Trichomes parallel within a fairly wide sheath; plant mass
developing bushy tufts; heterocysts basal in the trichome. Fig.
304 DESMONEMA

Fig. 304. Desmonema Wrangelii
(Ag.) Born. & Flah.

The falsely branched filaments
of this species differ from others
in the Scytonemataceae by hav-
ing several trichomes within 1
sheath. The filaments are gregarious and form plant masses of ma-
croscopic size on moist aerial substrates, and usually show erect tufts.
This is the only species reported from the United States.

Figure 304

420b Trichomes twisted and entangled in a wide sheath; heterocysts
intercalary. Fig. 305 DIPLOCOLON

Fig. 305. Diplocolon Heppii Naeg.
(Redrawn from Smith).

This plant forms an expanse on
moist aerial substrates such as drip-
ping rocky cliffs. The trichomes
are falsely branched, have inter-
calary heterocysts and are inclosed
several together in a wide gelatin-
P 3 nr ous sheath.

Figure 205 »»«*%*»**.

421a (376) Plants attached; cells club-shaped or with other shapes,
gregarious, forming cushion-like masses or horizontal expanses,
or solitary; epiphytic or growing on shells; cells usually showing
endospores (segments of the protoplast rounded up and forming
reproductive bodies which are spore-like) 422

421b Plants not attached; cells mostly spherical, hemispherical, or rod-
shaped, not forming cushion-like masses nor horizontal expanses;
endospores lacking 427

175

HOW TO KNOW THE FRESH-WATER ALGAE

422a Cells erect, subcylindrical clubs, straight or curved; epiphytic;
endospores cut off successively at the tips of cylindrical proto-
plasts. Fig. 306 CHAMAESIPHON

Fig. 306. Chamaesiphon incrustans Gru-
now.

These club-shaped or cylindrical plants
grow as epiphytes on filamentous algae
and whereas they may be solitary they
usually occur in gregarious patches. When
mature the end of the protoplast cuts off
rounded-up spores, "endospores" which
float away as regenerative elements.

Figure 306

422b Cells some other shape; gregarious, forming horizontal expanses
or cushions 423

423a Perforating shells, forming short irregular, spreading filaments
(filamentous character not clearly evident). Fig. 307 HYELLA

Fig. 307. Hyella fontana Huber
& Jadin.

Most species of this genus are
marine but some occur in fresh
water, boring into shells of mol-
luscs. The plant is a short, ir-
regularly branched filament, some-
times forming a cushion-like mass.
The substrate must be treated with dilute acetic acid to dissolve away
the lime before the plants can be studied satisfactorily.

423b Not perforating shells; plant mass expanded or cushion-like . . 424

Figure 307

424a Plant mass composed of cells arranged in 1 layer. Fig. 308 ....
XENOCOCCUS

Figure 308

Xenococcus Schousbei Thur.
are at least 2 species of this

Fig. 308

There

genus found in the fresh waters with-
in the United States, most forms be-
ing marine. They occur as patches of
blue-green cells, compactly arranged
as epiphytes on filamentous algae. Cells
form endospores although they may re-
produce actively by fission.

176

HOW TO KNOW THE FRESH-WATER ALGAE

424b Plant mass in the form of a cushion with cells arranged in ver-

x- i 425

tical rows wmM

425a Cells surrounded by a sheath; plant mass thick, cartilaginous,
usually macroscopic. Fig. 309 CHONDROCYSTIS

Fig. 309. Chondrocystis Schauinslandii
>. Lemm.

mm&smm

Figure 309

,0 : QLJ-5^KfQ[j^^: This species forms extensive, cushion-

Hlo^%V; ; :, like masses on exposed surfaces and

are heavily encrusted with lime. The
colonial mass is inclosed by a tough
mucilage in which 'families' of cells
are surrounded by individual sheaths.
This is the only species in the genus
and seems to have been reported but a few times from the United
States.

425b Cells not inclosed by a thick sheath; plant mass macroscopic . 426

426a Plant mass forming a flat, encrusting layer; cells forming short,
erect unbranched moments. Fig. 310 PLEUROCAPSA

Fig. 310. Pleurocapsa minor Hansg.

In this genus the plant mass is essen-
tially filamentous but the cells are so close-
ly oppressed that the branching habit can-
not be determined easily without dissect-
ing. Encrusting thralli are produced with
some differentiation between the lower or
inner cells and those near the surface
which produce the endospores.

Figure 310

426b Plant mass cushion-like; cells forming erect branched filaments.

Fig. 311 ONCOBYRSA

Fig. 311. Oncobyrsa sp. a, habit of col-
ony; b, diagram of cell arrangement.
Oncofyyrsa rivularis is the most com-
mon species of this genus. It has com-
pactly arranged series of cells in which
the filamentous plan can be more easily
determined than in Pleurocapsa (Fig.
310). The thallus is a mound of cells,
encased in a tough mucilage on fila-
mentous algae. Although the general
habit is that of members of Chamaesiphonaceae, there have been no
endospores observed.

177

Figure 31 1

HOW TO KNOW THE FRESH-WATER ALGAE

427a (421) Cells globose, or hemispherical because oi recent cell di-
vision 428

427b Cells some other shape 441

428a Cells inclosed in mucilage and bearing a long gelatinous hair.
See Fig. 206 GLOEOCHAETE

428b Cells not in a sheath which bears a hair 429

429a Protoplasts occurring as bright blue-green, vermiform bodies, medi-
ately arranged or scattered within Oocystis-like cells (see Oocy-
sts, Fig. 85), inclosed by mother-cell wall. See Fig. 208

GLAUCOCYST1S

429b Cells not as above.

430

430a Cells solitary or grouped in small families of 2-4-8 (rarely as many
as 16) individuals, if more than 16, then in a flat plate 431

430b Cells aggregate in larger numbers, inclosed by a mucilaginous
sheath 435

431a Cells solitary or in pairs, without a gelatinous sheath. Fig. 312.
SYNECHOCYST1S

Fig. 312. Synechocystis aquatilis Sauv.

This is a rather rare species which is prob-
ably of more common occurrence than is evi-
denced by the records of it from this country.
There are globular cells, solitary or in pairs,
without a mucilaginous sheath being appar-
ent. The densely granular 'central' body of
the cells is more complex than for other gen-
era in the Chroococcaceae.

Figure 312

431b Cells inclosed by a mucilaginous sheath (sometimes indistinct).
432

178

HOW TO KNOW THE FRESH-WATER ALGAE

CO CD

432a Cells arranged in rectilinear series to form a flat plate. Fig. 313.
MERISMOPEDIA

Fig. 313. a, Mehsmopedia elegans
var. major G. M. Smith; b, M. giau-
ca (Ehr.) Naeg.

There are several species on rec-
ord from the United States, differ-
entiated by cell shape, color, and
presence of vacuoles. The genus is
easily distinguishable by the definite
arrangement of the cells in rectilinear
series. M. convoiufa Breb. is an un-
common species which has relatively
large plates that are enrolled at the
margin.

000

ooooo

0000

ooooo
ooooo
ooooo

Figure 313

432b Cells not arranged in rectilinear series

433

433a Cells heart-shaped or round, occurring at the ends of radiating

strands of mucilage (focus down into the colony and cut down

illumination to detect presence of radiating strands). Fig. 314.

GOMPHOSPHAER1A

Fig. 314. a, Gomphosphaeria
aponina Kuetz.; b, G. lacustris
Chod.

• * 4

o o

°o<b

■ 9?o

y*

Figure 314

These plants are characterized
by having cells in globular colo-
nies, closely or distantly arranged
at the ends of mucilaginous
strands that radiate from the cen-
ter of the thallus. G. lacustris
is frequently found in the euplank-
ton, whereas G. aponina occurs
mostly in the tychoplankton.

433b Cells not at the ends of radiating strands 434

179

HOW TO KNOW THE FRESH-WATER ALGAE

434a Groups of cells inclosed in concentric layers of mucilage; colonial
investment intermingling (confluent) with sheaths of other groups
and so forming gelatinous masses, mostly on moist substrates;

sheaths showing definite concentric rings. Fig. 315

GLOEOCAPSA

.;:-■'->. Fig. 315. Gloeocapsa punctata Naeg.

: '/jr*" ■■ '•' "©©)'■'• ®- This is a genus in which globular

W..!%/( ^"Tgfc -^ cells are inclosed, many 'famiHes' to-

'^/^^"/XS \ gether within gelatinous masses of con-
W;i @.Vx?" N :'i siderable size. A common habitat is
Wi^VA/ipfv'J the surface of moist rocks and cliffs,
rS\"<--' VSJ£v -->--v '^. ' soil in greenhouses, moist cement work,
-.;,- <-::..s etc Cells, pairs of cells, or clusters

Figure 315 Q l ce \\ s are mc losed in concentric lay-

ers of mucilage. Many species, especially when few cells are in-
volved, can scarcely be differentiated from Chroococcus (Fig. 316) and
there is a disposition among some specialists to place the two genera
together.

434b Colonial mucilage not intermingling with that of other colonies;
families of cells separated from one another, usually free-floating
but commonly inhabiting soil and moist substrates in aerial situ-
ations; colonial sheath usually without conspicuous concentric

rings. Fig. 316 CHROOCOCCUS

/s=5f=^/^*p\ Fig. 316. a, Chroococcus Prescottii

Q^y^tP Drouet & Daily; b, C. limneticus

K^r^pK) var - distans G. M. Smith; c, C.

^ viA^y - limneticus Lemm.

There are numerous species in
this genus, many of them inade-
quately described and differenti-
al} ated. The genus is separated from
fy^JuC^) Gloeocapsa (Fig. 315) mostly on
^t_J ^ the basis of the fewness of cells
b & involved in a colony and by the
Figure 316 fact that 'families' of cells are not
all inclosed in a common lamellated mucilaginous matrix. The
colonies are usually composed of no more than 16 cells and more
commonly of but 4, 8 or 12 cells. A few species are definitely plank-
tonic but others occur attached to aquatic substrates or form films on
aerial surfaces. C. turgidus (Kuetz.) Naeg. is a large species in which
cells occur in 2's and 4's within a stratified envelope and is one that
is invariably found in desmid habitats where the water is acid.

435a (430) Cells arranged to form a flat plate 436

435b Cells forming irregularly globular or oval colonies 437

180

a

HOW TO KNOW THE FRESH-WATER ALGAE

436a. Cells arranged in rectilinear series. See Fig. 313

MERISMOPED1A

436b Cells irregularly arranged. Fig. 317 HOLOPEDIUM

(0 o

■;QO Q O0'OO«O«o o °o

ooo

o o

°o*

OOO On 8 W

o°°;

Fig. 317. Holopedium iriegulare Lag.

This genus differs from Merismopedia by-
having the cells irregularly arranged with-
in a gelatinous plate. Only this species
has been reported for the genus from the
United States.

Figure 31 7

437a (435) Colony globular, rather definite in shape 438

437b Colony irregular in outline 440

438a Cells very numerous and crowded within the colonial mucilage
(usually showing false vacuoles which refract the light so that the

cells appear brownish, black or purplish). Fig. 318

MICROCYSTIS

Fig. 318. a, Microcystis Hos-aquae
(Wittr.) Kirch.; b, M. aeruginosa
Kuetz. emend Elenkin.

&g|s|||^ 4%. «S^ iBk The marble-like cells of this

genus are closely compacted and
'*VJV irregularly arranged in definite-

ly shaped but irregular colonies
W% inclosed in mucilage. M. Hos-

aquae has more nearly globular
and symmetrically shaped colo-
b nies than M. aeruginosa. The cells

Figure 318 often contain pseudovacuoles (gas

pockets) and float high in the
water. Hence they produce surface scums and like Aphanizomenon
(Fig. 298) cause a great deal of disturbance in lakes and reservoirs.
Dense growths may lead indirectly to the death of fish through suf-
focation. It is rather curious that where these species occur (especial-
ly M. aeruginosa) the water is completely dominated by the plant to
the exclusion of almost all other forms. It has often been noted that a
lake may be densely overgrown with either Microcystis ox with Aphani-
zomenon, but not the two together. There are several species of the
genus differentiated by size and by details of the sheath structure, and
by form of colony.

181

HOW TO KNOW THE FRESH-WATER ALGAE

438b Cells not densely crowded but evenly spaced or regularly ar-
ranged 439

°&® o (

439a Cells in one layer at the periphery of the mucilage. Fig. 319.
COELOSPHAERIUM

Fig. 319. a, Coelosphaerium Naegeli-
anum Unger; b, C. Kuetzingianum
Naeg.

There are 2 common species of this
genus which are members of the
open water plankton. As the name
suggests, the cells are arranged so
as to form a hollow colony. C. Nae-
gelianum has cells which contain
pseudovacuoles which are light re-
fractive and the colony appears
brownish-purple or even black rather
than blue-green when seen micro-
scopically.

Figure 319

439b Cells distributed throughout the colonial mucilage. Fig. 320 ....

APHANOCAPSA

Q

03

-•'• o o
n ° P) o '•

% ° ft o°

8o\° oo

n O ^ OO-

Oq O C9
. o<b o

Fig. 320. a, Aphanocapsa Gie-
villei (Hass.) Rab.; b, A. elach-
ista West & West.

Whereas Microsystis has
cells compactly arranged, in
this genus they are rather even-
ly spaced throughout the colo-
nial mucilage. The cells are
spherical and vary in size in
different species, some being
not much larger than bacteria

and can be mistaken for them. Cells often appear in pairs. There are

several species reported from the United States.

Figure 320

440a (437) Cells crowded, usually with refractive false vacuoles. See
Fig. 318 MICROCYSTIS

440b Cells evenly spaced within the mucilage; false vacuoles lacking.
See Fig. 320 APHANOCAPSA

182

HOW TO KNOW THE FRESH-WATER ALGAE

441a (427) Cells quadrangular, arranged in flat plates. Fig. 321

TETRAPEDIA

Fig. 321. Tetrapedia sp., diagram showing
arrangement of rectangular cells.

Tetrapedia Reinschiana Arch, is a rare
plant that has quadrangular cells arranged
in multiples of 4 to form a flat rectangular
plate. One other species has been reported
from the United States, occurring in the plank-
ton.

Figure 321

441b Cells some other shape

442

442a Cells solitary or in colonies of few cells, up to 32

443

442b Cells numerous within a globular or amorphous gelatinous matrix.

448

443a Without a gelatinous sheath. Fig. 322 SYNECHOCOCCUS

Fig. 322. Synechococcus aeruginosus
Naeg.

This is a solitary unicell which does
not possess a gelatinous sheath. Cells
may be in pairs as a result of recent
fission. They are relatively large for
Cyanophyta (may be up to 35 microns
in length) and are often conspicuous in
the microscope mount because of their
briaht blue color.

Figure 322

443b With a gelatinous sheath (sometimes discerned with difficulty),
or inclosed by a gelatinous matrix 444

183

HOW TO KNOW THE FRESH-WATER ALGAE

444a Cells elongate; pointed at the ends. Fig. 323

DACTYLOCOCCOPS1S

Fig. 323. a, Dactylococcopsis acicularis
Lemm.; b, D. fascicularis Lemm.

These are fusiform shaped cells ar-
ranged with their long axes mostly-
parallel with that of the fusiform-shaped
colonial envelope. Two species are
known from this country, occurring in
the plankton.

Figure 323

444b Cells not pointed at the ends 445

445a Cells heart-shaped, at the ends of radiating strands of mucilage;
colonies globular. See Fig. 314 GOMPHOSPHAERIA

445b Cells not at the ends of radiating strands 446

446a Cells radiately disposed. Fig. 324 MARSSONIELLA

Fig. 324. Maissoniella elegans Lemm.

This species (the only one reported) has
pear-shaped cells more or less definitely
arranged about a common center with
scarcely any evidence of a colonial muci-
lage. It is to be looked for in the plank-
ton of open water.

Figure 324

446b Cells not radiately arranged 447

184

HOW TO KNOW THE FRESH-WATER ALGAE

447a Individual cell sheath distinct. Fig. 325 GLOEOTHECE

Fig. 325. Gloeofhece linearis Naeg.

In this genus the cells are elongate
cylinders or bacilliform in shape and
are inclosed by individual sheaths all
within a common mucilage. There are
several species differentiated mostly by
cell shape and size. Species should be
compared with Aphanothece (Fig. 327).

vxy&i

<=o

.°o

■c?.

m

CG

,8 #

Figure 325

447b Indivi4ual cell sheath not apparent. Fig. 326 ... RHABDODERMA

Figure 326

Fig. 326. Rhabdodeima lineare

Schm. & Lauterb.

In this genus the cells are
elongate and cylindrical, even
vermiform and are much like
Gioeofhece except that there is no
individual cell sheath. The plants
occur in small colonies of 4, 8, or
16 in the plankton of lakes; is
sometimes in the tychoplankton.

448a (442) Cells arranged at the periphery of a gelatinous matrix. See
Fig. 319 .COELOSPHAER1UM

448b Cells irregularly scattered throughout the colonial mucilage . . . 449

449a Individual cell sheath not distinct. Fig. 327 APHANOTHECE

Fig. 327. Aphanothece Castagnei
(Breb.) Rab.

Cells are elongate cylinders or
bacilliform, occurring in large co-
lonies up to 5 cm. in diameter and
.have no individual sheaths. The
colonies develop on the bottom
of lakes but become free-floating
and are often washed into shallow water along shore where they may
form a 'soupy' mass of brownish or olive-green (rarely bluish) bodies.
Macroscopically they appear much like Nostoc colonies (Fig.. 300) espe-
cially if the colonies are young and smooth in outline.

449b Individual cell sheath distinct. See Fig. 325 GLOEOTHECE

185

HOW TO KNOW THE FRESH-WATER ALGAE

450a (345) Shells mostly circular or polygonal in outline (sometimes

irregular), but with decorations (rows of dots, lines, etc.) which

are concentrically arranged from a central point; raphe (distinct

canal in wall in the median region) absent. Figs. 328 and 329.

CENTRALES*

Fig. 328. Melosira granulata (Ehr.) Ralfs.

Figure 328

Fig. 329. Stephanodiscus niagarae Ehr.

Figure 329

1

Figure 330

450b Shells mostly elongate, ci-
gar-shaped,, boat-s h a p e d,
crescent-shaped, or rectan-
gular, with decorations bi-
laterally arranged from longi-
tudinal lines; raphe (distinct
longitudinal canal in the
wall in the median region)
present or absent. Figs. 330
to 337 PENNALES*

Fig. 330. Fragilaria sp.

*ln order to identify diatoms satisfactorily special techniques are required for pre-
paring them for microscopical study, and a descriptive key must of necessity employ
highly specialized terminolcgy. Space here does not permit the inclusion of all of the
common diatom genera which occur in fresh water (which may number 50 or more).
Hence a key which does not include all or most of them would be inadequate and
actually misleading in many instances. A few of the more common genera, especially
those found in the phytoplankton of lakes, are illustrated.

186

HOW TO KNOW THE FRESH-WATER ALGAE

Diatoms occur in innumerable species both in the plankton, on the
bottom, and on submerged aquatics, etc. The cells should be cleaned
by boiling in acid so as to remove all organic content in order to make
the wall characters visible. Identification of genera and species is
based largely upon the shape of the cell and upon the manner of
decoration, the presence of septae in the cells, and upon other details
which cannot be seen unless the shells are clear and free from chroma-
tophores and oil droplets. Some are so characteristically shaped that
the genus can be determined without this treatment. The most com-
mon genera in the plankton are Stephanodiscus, Melosira, Fragilaria,
Asterionella, Navicula and Tabellaria. Stephenodiscus is shaped like
a drum; has a crown of short spines just within the margin. Melosira
is capsule-shaped, with the cells arranged end to end in filaments.
Fragilaria commonly has long, narrow rectangular cells placed side
by side to form flat ribbons. Tabellaria forms zig-zag chains. Navicula
is commonly 'boat-shaped' or cigar-shaped when the cell is seen in
valve (top) view. Asterionella has cells radiating from a common center
in one plane.

Fig. 331. Tabellaria fenestrata (Lyngb.) Kuetz.

Figure 331

Fig. 332. Meridion circulare (Grev.) Ag.

Fig. 333. Asterionella iormosa Hass.

Figure 332

Figure 333

187

HOW TO KNOW THE FRESH- WATER ALGAE

Fig. 334. Navicula sp.; a, top (valve) view; b, side (girdle) view.

c

-

h ; iflU

] . ..

w

1

-r\

1

Figure 334

Fig. 335. Gomphonema sp.

Figure 335

Fig. 336. Surirella splendida (Ehr.) Kuetz.

Fig. 337. Cocconeis Pediculus Ehr.

Figure 336

Figure 337

188

A CHECK LIST OF THE MORE COMMON GENERA

OF FRESH-WATER ALGAE ACCORDING TO

FAMILIES, ORDERS AND PHYLA

I. PHYLUM (DIVISION) CHLOROPHYTA

A. SUB-DIVISION CHLOROPHY-
CEAE

1. Order Volvocales

Family Polyblepharidaceae
Dunaliella

p. 38, fig. 32
Polyblepharides

p. 35, fig. 29
Pyramimonas

p. 35, fig. 30
Stephanoptera

p. 35, fig. 31
Family Chlamydomonada-

ceae
Carteria

p. 31, fig. 21
Chlamydomonas

p. 34, fig. 27
Chlorogonium

p. 33, fig. 25
Lobomonas

p. 33, fig. 26
Platymonps

p. 31, fig. 20
Sphaerellopsis

p. 34, fig. 28
Family Phacotaceae
Phacotus

p. 32, fig. 23
Pteromonas

p. 33, fig. 24
Scotiella

p. 84, fig. 127
Wislouchiella

p. 32, fig. 22
Family Volvocaceae
Eudorina

p. 29, fig. 17

Gonium

p. 26, fig. 10
Pandorina

p. 28, fig. 14
Platydorina

p. 26, fig. 9
Pleodorina

p. 30, fig. 18
Volvox

p. 28, fig. 15
Family Spondylomoraceae
Chlamydobotrys

p. 27, fig. 13
Pascheriella

p. 27, fig. 11
Spondylomorum

p. 27, fig. 12
Family Sphaerellaceae
Haematococcus

p. 30, fig. 19
Stephanosphaera

p. 29, fig. 16

2. Order Tetrasporales

Family Palmellaceae
Asterococcus

p. 46, fig. 51
Dispora

p. 49, fig. 58
Gloeocystis

p. 41, fig. 41
Hormotila

p. 99, fig. 154
Palmella

p. 38, fig. 36
Palmodictyon

p. 43, fig. 45
Sphaerocystis

p. 48, fig. 54

189

HOW TO KNOW THE FRESH-WATER ALGAE

Urococcus

p. 82, fig. 124
Family Tetrasporaceae
Apiocystis

p. 39, fig. 37
Schizochlamys

p. 45, fig. 48
Tetraspora

p. 38, fig. 35
Family Chlorangiaceae
Chlorangium

p. 52, fig. 63
Malleochloris

p. 67, fig. 95
Prasinocladus

p. 100, fig. 156
Stylosphaeridium

p. 67, fig. 96
Family Coccomyxaceae
Chlorosarcina

p. 37, fig. 34
Coccomyxa

p. 40, fig. 39
Dactylothece

p. 44, fig. 47
Elakatothrix

p. 39, fig. 38
Nannochloris

p. 78, fig. 116
Ourococcus

p. 64, fig. 89

3. Order Ulotrichales

Family Ulotrichaceae
Binuclearia

p. 105, fig. 164
Geminella

p. 106, fig. 165
Hormidiopsis

p. 105, fig. 163
Hormidium

p. 107, fig. 168
Radiofilum

p. 106, fig. 166
Stichococcus

p. 104, fig. 162
Ulothrix

p. 107, fig. 167

Uronema

p. 108, fig. 169
Family Microsporaceae
Microspore!

p. 109, fig. 172
Family Cylindrocapsaceae
Cylindrocapsa

p. 108, fig. 170
Family Chaetophoraceae
Aphanochaete

p. 104, fig. 161
Chaetonema

p. 113, fig. 178
Chaetopeltis

p. 114, fig. 179
Chaetophora

p. 122, fig. 196
Chlorotylium

p. 117, fig. 186
Draparnaldia

p. 123, fig. 197
Draparnaldiopsis

p. 123
Entocladia

p. 112, fig. 175
Microthamnion

p. 120, fig. 191
Protoderma

p. 114, fig. 180
Pseudoulvella

p. 115, fig. 181
Pseudochaete

p. 112, fig. 176
Stigeoclonium

p. 113, fig. 177

Ulvella

p. 115, fig. 182

Family Protococcaceae
Protococcus
p. 53, fig. 66

Family Coleochaetaceae
Chaetosphaeridium
p. 51, fig. 62

Coleochaete
p. 97, fig. 150

Dicranochoete
p. 51, fig. 61

190

HOW TO KNOW THE FRESH-WATER ALGAE

Family Trentepohliaceae
Cephalemos

p. 115, fig. 183
Ctenocladus

p. 118, fig. 188
Fiidaea

p. 121, fig. 194
Gomontia

p. 116, fig. 184
Gongrosira

p. 117, fig. 185
Leptosira

p. 117, fig. 187
Trentepohlia

p. 109, fig. 171
Family Cladophoraceae
Aegagropila

p. 121, fig. 193
Basicladia

p. 119, fig. 190
Cladophoia

p. 120, fig. 192
Pithophora

p. 118, fig. 189
Rhizoclonium

p. 102, fig. 158
Family Sphaeropleaceae
Sphaeroplea

p. 103, fig. 160

4. Order Oedogoniales

Family Oedogoniaceae
Bulbochaete

p. 122, fig. 195
Oedocladium

p. Ill, fig. 174
Oedogonium

p. 102, fig. 159

5. Order Ul vales

Family Schizomeridaceae
Schizomeris
p. 101, fig. 157
Family Ulvaceae
Enteromorpha

p. 98, fig. 152
Monosfroma
p. 97, fig. 151

6. Order Schizogoniales

Family Schizogoniaceae
Prasiola

p. 98, fig. 153
Schizogonium

p. 92, fig. 140

7. Order Chlorococcales

Family Chlorococcaceae
Acanthosphaera

p. 79, fig. 117V 2
Chlorococcum
p. 42, fig. 42
Desmatractum
p. 68, fig. 97
Golenkinia

p. 61, fig. 84
Myrmecia

p. 81, fig. 122
Trebouxia
p. 80, fig. 121
Family Endosphaeraceae
Chlorochytrium
p. 66, fig. 94
Kentrosphaera

p. 84, fig. 126 Vz
Rhodochytrium
p. 66, fig. 93
Family Botryococcaceae
Botryococcus
p. 45, fig. 49
Family Characiaceae
Actidesmium

p. 59, fig. 80
Characium
p. 63, fig. 87
Family Hydrodictyaceae
Euastropsis

p. 36, fig. 33
Hydrodictyon

p. 54, fig. 69
Pediastrum

p. 55, fig. 70

Sorastrum

p. 60, fig. 82

Family Coelastraceae

Coelastrum

p. 58, fig. 77

191

HOW TO KNOW THE FRESH-WATER ALGAE

Schioederia
p. 64, fig. 88

Selenastrum
p. 53, fig. 67

Tetraedion

Family Oocystaceae
Ankistrodesmus
p. 54, fig. 68
Bohlinia

p. 80, fig. 120
Cerasterics

p. 86, fig. 130
Chlorella

p. 65, fig. 91
Closteridium

p. 65, fig. 90
Closteriopsis

p. 69, fig. 98
Dactylococcus
p. 52, fig. 65
Dictyosphaerium

p. 47, fig. 53
Dimorphococcus

p. 47, fig. 52
Echinosphaerella
p. 78, fig. 117
Eremosphaera

p. 81, fig. 123
Excentrosphaera
p. 83, fig. 126
Franceia

p. 56, fig. 73
Gloeotaenium
p. 61, fig. 83
Kirchneriella

p. 49, fig. 56
Lagerheimia

p. 79, fig. 118
Nephrocytium
p. 50, fig. 59
Oocystis

p. 62, fig. 85

Pachycladon
p. 85, fig. 128

Palmellococcus
p. 82, fig. 125

Planktosphaeria
p. 48, fig. 55

Polyedriopsis
p. 86, fig. 129

Quadrigula
p. 50, fig. 60

p. 87, fig. 131
Treubaria

p. 87, fig. 132
Trochiscia

p. 80, fig. 119
Westella

p. 60, fig. 81
Family Scenedesmaceae
Actinastrum

p. 58, fig. 78
Coronastium

p. 42, fig. 43
Crucigenia

p. 56, fig. 72
Errerella

p. 57, fig. 76
Micractinium

p. 57, fig. 75
Pectodictyon

p. 43, fig. 44
Scenedesmus

p. 57, fig. 74
Tetradesmus

p. 59, fig. 79
Tetrallantos

p. 49, fig. 57
Tetrastrum

p. 55, fig. 71

8. Order Siphonales

Family Phyllosiphonaceae
Phyllosiphon
p. 66, fig. 92
Family Dichotomosiphona-
ceae
Dichotomosiphon
p. 123, fig. 198

9. Order Zygnematales (Con-
jugales)

Family Zygnemataceae
Debarya

p. 96, fig. 149

192

HOW TO KNOW THE FRESH-WATER ALGAE

Mougeotia

p. 94, fig. 145
Mougeotiopsis

p. 96, Fig. 148
Pleurodiscus

p. 94, fig. 144
Sirogonium

p. 95, fig. 146
Spirogyra

p. 95, fig. 147
Zygnema

p. 93, fig. 142
Zygnemopsis

p. 92, fig. 141
Zygogonium
p. 93, fig. 143
Family Mesotaeniaceae
Cylindrocystis

p. 71, fig. 103
Genicularia

p. 72, Fig. 106
Gonatozygon

p. 73, fig. 107
Mesotaenium

p. 44, fig. 46
Netrium

p. 73, fig. 108
Roya

p. 73, fig. 109
Spiiotaenia
p. 72, fig. 105
Family Desmidiaceae
Arthiodesmus

p. 76, fig. 114
Closterium

p. 63, fig. 86
Cosmarium

p. 76, fig. 113
Cosmocladium
p. 46, fig. 50
Desmidium
p. 90, fig. 138

Docidium

p. 71, fig. 101
Euastrum

p. 75, fig. Ill
Gymnozyga

p. 90, fig. 136
Hyalotheca

p. 90, fig. 137
Micrasterias

p. 74, fig. 110
Onychonema

p. 88, fig. 133
Oocardium

p. 99, fig. 155
Penium

p. 72, fig. 104
Phymatodocis

p. 91, fig. 139
Pleuiotaenium

p. 71, fig. 102
Sphaerozosma

p. 89, fig. 134
Spondylosium

p. 89, fig. 135
Staurastrum

p. 75, fig. 112
Tetmemoius

p. 69, fig. 99
Triploceras

p. 70, fig. 100
Xanthidium
p. 77, fig. 115

B. SUB-DIVISION CHARACEAE

Chareae
Chaia

p. 21, fig. 2
Nitelleae
Nitella

p. 21, fig. 3
Tolypella
p. 20, fig. 1

II. PHYLUM (DIVISION) EUGLENOPHYTA

1. Order Euglenales Lepocinclis

Family Euglenaceae P- 25, fig.

Euglena Phacus

p. 25, fig. 8 p. 24, fig.

193

HOW TO KNOW THE FRESH-WATER ALGAE

Trachelomonas
p. 24, fig. 5

Family Colaciaceae
Colacium
p. 52, fig. 64

III. PHYLUM (DIVISION) PYRRHOPHYTA

A. SUB-DIVISION CRYPTOPHY-
CEAE

Family Cryptochrysidaceae
Chroomonas

p. 150, fig. 254
Family Cryptomonadaceae

p. 150, fig. 255

B. SUB-DIVISION DINOPHYCEAE

Order 1. Dinokontae

Family Gymnodiniaceae
Gymnodinium
p. 151, fig. 257
Family Gonyaulacaceae
Gonyaulax
p. 152, fig. 259
Family Glenodiniaceae
Glenodinium
p. 153, fig. 261

Hemidinium
p. 153, fig. 260
Family Peridiniaceae
Peridinium

p. 152, fig. 258
Family Ceratiaceae
Ceratium

p. 151, fig. 256

Order 2. Dinococcales

Family Dinococcaceae
Cystodinium

p. 149, fig. 253
Raciborskia

p. 149, fig. 252
Tetradinium

p. 149, fig. 251

IV. PHYLUM (DIVISION) CHLOROMONADOPHYTA

Gonycstomum
p. 23, fig. 4

V. PHYLUM (DIVISION) CHRYSOPHYTA

A. SUB-DIVISION XANTHOPHY-
CEAE (HETEROKONTAE)

1. Order Heterocapsales
Family Heterocapsaceae

Chlorosaccus
p. 142, fig. 238

2. Order Heterococcales
Family Pleurochloridaceae

Arachnochloris
p. 140, fig. 232

Botrydiopsis
p. 137, fig. 224

Chlorallantus
p. 141, fig. 234

Chlorocloster

p. 139, fig. 230
Diachros

p. 136, fig. 223
Goniochloris

p. 142, fig. 237
Monallantus

p. 138, fig. 227
Perone

p. 133, fig. 216
Pleurogaster

p. 139, fig. 229
Tetragoniella

p. 141, fig. 236

194

HOW TO KNOW THE FRESH-WATER ALGAE

Trachychloron
p. 141, fig. 235
Family Botryochloridaceae
Chlorellidiopsis
p. 143, fig. 240
Uncertain Position
Leuvenia

p. 137, fig. 225
Family Centritractaceae
Bumilleriopsis

p. 138, fig. 228
Centritractus

p. 139, fig. 231
Pseudotetraedion
p. 137, fig. 226
Family Characiopsidaceae
Characiopsis

p. 133, fig. 217
Peromelia

p. 135, fig. 220
Family Gloeobotrydaceae
Chlorobotrys

p. 136, fig. 222
Gloeobotrys
p. 143, fig. 239
Family Chlorotheciaceae
Chlorothecium

p. 133, fig. 215
Ophiocytium
p. 134, fig. 219
Family Meringosphaera-
ceae
Meringosphaera
p. 140, fig. 233
Family Mischococcaceae
Mischococcus
p. 130, fig. 210

3. Order Heterotrichales

Family Heterotrichaceae
Bumilleria

p. 132. fig. 213
Monocilia

p. 131, fig. 211
Tribonema

p. 131, fig. 212

4. Order Heterochloridales
Family Chloramoebaceae

Chlorochromonas
p. 135, fig. 221

5. Order Rhizochloridales

Family Stipitococcaceae
Stipitococcus
p. 134, fig. 218

6. Order Heterosiphonales

Family Botrydiaceae
Botrydium

p. 132, fig. 214
Family Vaucheriaceae
Vaucheria

p. 124, fig. 199
B. SUB-DIVISION CHRYSOPHY-
CEAE

1. Order Chrysomonadales

Family Mallomonadaceae
Chrysosphaerella

p. 154, fig. 262
Mallomoncts

p. 147, fig. 248
Family Syncryptaceae
Derepyxis

p. 147, fig. 247
Family Synuraceae
Synura

p. 154, fig. 263
Family Ochrpmonadaceae
Chlorochromonas

p. 135, fig. 221
Cyclonexis

p. 155, fig. 265
Dinobryon

p. 145, fig. 243
Hyalobryon

p. 146, fig. 244
Uroglenopsis

p. 155, fig. 264

2. Order Rhizochrysidales

Family Rhizochrysidaceae
Chrysamoeba

p. 148, fig. 250
Chrysidiastrum

p. 156, fig. 266
Chrysostephanosphaera

p. 157, fig. 269

195

HOW TO KNOW THE FRESH-WATER ALGAE

Lagynion

p. 147, fig. 246
Rhizochrysis

p. 148, fig. 249

3. Order Chrysocapsales
Family Chrysocapsaceae

Chrysocapsa

p. 157, fig. 268
Phaeosphaera

p. 156, fig. 267
Family Hydruraceae
Hydrurus

p. 144, fig. 241

4. Order Chrysosphaerales
Family Chrysotomataceae

Chrysostrella
p. 146, fig. 245

5. Order Chrysotrichales
Family Phaeothamniaceae

Phaeothamnion
p. 144, fig. 242

SUB-DIVISION BACILLARIO-

PHYCEAE

1. Order Centrales

Family Coscinodiscaceae
Melosiia

p. 186, fig. 328

Stephanodiscus
p. 186, fig. 329

2. Order Pennales

Family Fragilariaceae
Asterionella

p. 187, fig. 333
Fragilaria

p. 186, fig. 330
Tabellaria-
p. 187, fig. 331
Family Achnanthaceae
Cocconeis
p. 188, fig. 337
Family Gomphonemataceae
Gomphonema
p. 188, fig. 335
Family Meridionaceae
Meridion

p. 187, fig. 332
Family Naviculaceae
Navicuia

p. 188, fig. 334
Family Surirellaceae
Surirella

p. 188, fig. 336

VI. PHYLUM (DIVISION) CYANOPHYTA

A. SUB-DIVISION MYXOPHY-
CEAE
1. Order Chroococcales

Family Chroococcaceae
Aphanocapsa

p. 182, fig. 320
Apanothece

p. 185, fig. 327
Chondrocystis

p. 177, fig. 309
Chroococcus

p. 180, fig. 316
Coelosphaeiium

p. 182, fig. 319
Dactylococcopsis

p. 184, fig. 323
Glaucocystis

p. 129, fig. 208

Gloeocapsa

p. 180, fig. 315
Gloeochaete

p. 128, fig. 206
Gloeothece

p. 185, fig. 325
Gomphosphaeria

p. 179, fig. 314
Holopedium

p. 181, fig. 317
Marssoniella

p. 184, fig. 324
Merismopedia
' p. 179, fig. 313
Microcystis

p. 181, fig. 318
Rhabdoderma

p. 185, fig. 326

196

HOW TO KNOW THE FRESH-WATER ALGAE

Synecococcus

p. 183, fig. 322
Synechocystis

p. 178, fig. 312
Tetrapedia

p. 183, fig. 321

2. Order Chamaesiphonales

Family Chamaesiphonaceae
Chamaesiphon

p. 176, fig. 306
Family Pleurocapsaceae
Hyella

p. 176, fig. 307
Oncobyrsa

p. 177, fig. 311
Pleurocapsa

p. 177, fig. 310
Xenococcus

p. 176, fig. 308

3. Order Hormogonales

Family Oscillatoriaceae
Arthrospira

p. 159, fig. 273
Dasygloea

p. 165, fig. 284

Hydrocoleum
p. 164, fig. 282

Lyngbya

p. 159, fig. 272

Microcoleus
p. 164, fig. 283

Oscillatoria
p. 161, fig. 277

Phormidium
p. 163, fig. 281

Porphyrosiphon
p. 162, fig. 279

Schizothrix
p. 165, fig. 285

Spirulina

p. 158, fig. 270

Trichodesmium
p. 162, fig. 278

Family Nostocaceae
Anabaena

p. 158, fig. 271
Anabaenopsis

p. 171, fig. 296
Aphanizomenon

p. 172, fig. 298
Aulosira

p. 173, fig. 301

Cylindrospermum

p. 170, fig. 295
Nodularia

p. 172, fig. 299
Nostoc

p. 173, fig. 300
Wollea

p. 171, fig. 297

Family Stigonemataceae
Capsosiia

p. 168, fig. 291
Hapalosiphon

p. 169, fig. 293
Nostochopsis

p. 168, fig. 290
Siigonema

p. 169, fig. 292

Family Scytonemataceae
Desmonema

p. 175, fig. 304
Diplocolon

p. 175, fig. 305
Microchaete

p. 170, fig. 294

Piecfonema

p. 161, fig. 276

Scytonema

p. 174, fig. 302

Tolypothrix
p. 174, fig. 303

Family Rivulariaceae
Amphithrix

p. 160, fig. 274

Calothrix

p. 160, fig. 275

Dichothrix

p. 167, fig. 289

197

HOW TO KNOW THE FRESH-WATER ALGAE

Gloeotrichia
p. 166, fig. 287

Rivularia

p. 167, fig. 288

Sacconema
p. 166, fig. 286

B. SUB-DIVISION CHLOROBAC-
TERIACEAE

VII. PHYLUM RHODOPHYTA

A. SUB-DIVISION PROTOFLORI-
DEAE

Family Goniotrichaceae
Asterocystis
p. 129, fig. 207
Family Bangiaceae
Bangia

p. 127, fig. 205
Family Erythrotrichaceae
Compsopogon
p. 126, fig. 203
Uncertain Position
Porphyridium
p. 130, fig. 209

B. SUB-DIVISION FLORIDEAE
Family Chantransiaceae
Audouinella

p. 127, fig. 204
Batiachospermum
p. 110, fig. 173
Family Lemaneaceae
Lemanea

p. 124, fig. 200
Tuomeya
p. 126, fig. 202
Family Thoreaceae
Thorea

p. 125, fig. 201

198

INDEX AND PICTU RED-GLOSSARY

Acanthosphaera 79

Zachariasi 79
ACICULAR: needle-like in

shape. Fig. 338

Figure 338

ACID BOG: having soft wa-
ter, low or lacking in dis-
solved minerals; pH below
neutral (7.0).

Acrochaetium 1 27

Actidesmium 59
Hookeri 59

Actinastrum 58
gracillimum 58
Hantzschii 58

Aegagropila 121
profunda 121

AERIAL, algal habitat on
moist soil, rocks, trees,
etc.; involving a thin film
of water; subaerial, some-
what or sometimes aerial.

AKINETE: a type of spore
formed by the transfor-
mation of a vegetative
cell into a thick-walled
resting cell, containing a
concentration of food ma-
terial.

Alcohol

food reserve 9, 1 1
preservative 16

ALKALINE WATER: con-
taining a predominating
amount of hydroxyl-ions
as compared with hydro-
gen-ions; abundant in
electrolytes; hard water
lakes ordinarily are al-
kaline

Alligator 13

ALPINE: altitudes above
tree line (usually).

AMOEBOID: like an amoe-
ba; creeping by extensions
of highly plastic proto-
plasm (pseudopodia).

AMORPHOUS:, without defi-
nite shape; without regu-
lar form.

Amphithrix 160
janthina 1 60

Anabaena 158, 172, 173;

also 6, 160, 162

spiroides var. crassa 1 58

subcylindrica 1 58
Anabaenopsis 171

Elenkenii 171
ANASTOMOSE: to separate

and come together again;

a meshwork. Fig. 339

Figure 339

Angiosperms 116, 118

ANISOGAMETE: a sex cell
which shows only slight
differentiation in respect
to maleness or female-
ness.

Ankistrodesmus 54, 59, 62,
64, 69; also 14
Braunii 54
convolutus 54
falcatus 54
■fractus 54
spiralis 54

ANTAPICAL: the posterior
or rear pole or region of
an organism, or of a col-
ony of cells.

ANTERIOR: the forward
end; toward the top.

ANTHERIDIUM: a single
cell or a series of cells in
which male gametes are
produced; a multicellular
globular male reproductive
organ in the Characeae.
(See Fig. 159)

ANTHEROZOID: male sex
cell or gamete.

APEX: the summit; the ter-
minus; end of a projection
or of an incision.

Aphanizomenon 172; also
181
ilos-aquae 172

Aphanocapsa 182
elachista 1 82
Grevillei 1 82

Aphanochaete 104, 113
polychaete 1 04
repens 1 04

Aphanothece 185
Castagnei 185

APICAL: the forward or an-
terior end; the top.

Apiocystis 39
Brauniana 39

APLANOSPORE: non-motile,
thick-walled spore formed
many within an unspecial-
ized vegetative cell; a
small resting spore.

Araceae 66

Arachnochloris 1 40
minor 1 40

ARBUSCULAR: branched or
growing like a tree or
bush.

ARCUATE: curved, bow-
shaped. Fig. 340

Figure 340

Arisaema 1 3
ARMORED: see thecate.
Arthrodesmus 76

incus 76
Arthrospira 159

Jenneri 1 59
Astasia 23
Asterionella 187; also 186

formosa 187
Asterococcus 46,

limneticus 46

superbus 46
Asterocystis 1 29

smaragdina 1 29
ATTENUATE: narrowing

a point or becoming

duced in diameter.

341

81

to

re-
Fig.

Figure 341

Audouinella 127
violacea 1 27

Aulosira 173
laxa 173

AUTOSPORES: spore - I i k e
bodies cut out of the con-
tents of a cell which are
small replicas of the par-
ent cell and which only
enlarge to become ma-
ture plants.

AXIAL: along a median line
bisecting an object either
transversely or longitudi-

199

HOW TO KNOW THE FRESH-WATER ALGAE

nally (especially the latter.
e.g., an axial chloroplast).
Fig. 342

f**H*PEEJ*(

Calothrix 160, 167

atricha 1 60

Braunii 1 60

epiphytica 1 60

CAPITATE: with an

enlarge-

ment or a head

at one

end. Fig. 343

Figure 342

B

BACILLIFORM: rod-shaped.
Bangia 1 27

fuscopurpurea 1 27
Basictadia 1 1 9

Chelonum 1 1 9

BASIC WATER: hard water

containing an abundance

of dissolved minerals or

chemical elements.
Batrachospermum 110, 125;

also 22, 127

Boryanum 1 1

moniliforme 1 1

vagum 1 1

BILOBED: with two lobes or

extensions.
Binuclearia 105

tatrana 105

BIPAPILLATE: with two
small protrusions; nipples.

BISCUIT-SHAPED: a thick-
ened pad; pillow-shaped

BIVALVE (wall): wall of a
cell which is in two sec-
tions, one usually slight-
ly larger than the other.
(See Melosira, Fig. 328)

Bladderwort: see Utnculoria.

BLEPHAROPLAST: a granu-
lar body in a swimming
organism from which a
flagellum (organ of loco-
motion) arises.

BLOOM: see Water Bloom.

Blue-green Algae 6

Bohlinia 80, 84
echidna 80

Botrydiopsis 137, 143
arhiza 1 37
eriensis 1 37

Botrydium 132, also 22
granulation 132
Wallrothii 132'

Botryococcus 45, 129; also
22
Braunii 45

BRISTLE: a stiff hair; a
needle-like spine.

Brown Algae, see Phaeophy-
ta

Bulbochaete 122; also 102
congener 122
insignis 1 22

Bumilleria 1 32
exiJis 132
sicula 1 32

Bumilleriopsis 1 38
brev/s 1 38

Figure 343

Capsosira 1 68
Brebissonii 168

CAROTENE: orange - yellow
plant pigment of which
there are four kinds in
algae; a hydrocarbon,
C H. .

CARPOGONIUM: female sex
organ in the red algae;
a flask-shaped cell with
a long, hair-like exten-
sion, the trichogyne.

Carteria 3 1

cordiformis 31
Klebsii 31

CARTILAGINOUS: tough but
pliable; resilient.

CELLULOSE: a n insoluble

carbohydrate, C H O . of
6 10 5'

which most plant cells

are composed.
CENTRAL BODY: the central

region of a blue-green al-
gal cell, relatively unpig-

mented and containing

nuclear granules.
CENTRALES: a subclass of

the Diatomaceae which

includes cells with radial

symmetry and radiately

disposed wall markings;

cells round in end view,

186.
Centritractus 1 39

belanophorus 1 39
Cephaleuros 115; also 13, 22

virescens 1 1 5
Cerasterias 86

irregulare 86
Ceratium 1 51

hirundinella 1 51
Ceratophyllum 166
Chaetonema 1 1 3

irregulare 1 1 3
Chaetopeltis 1 1 4

orbicularis 1 1 4
Chaetophora 122; also 113,

123

elegans 122

incrassata 122
Chaetosphaeridium 51, 67,

99

globosum 51

Chamaesiphon 1 76

incrustans 1 76
Chamaesiphonaceae 177
Chantransia 1 27
Chara 21; also 20

canescens 21

coronata 21

excelsa 21
Characeae 1 , 6, 20
Characiopsis 133, 135; also

63, 68, 134

acuta 133

cylindrica 1 33

spinifer 133
Characium 63, 68; also 133,

134

Debaryanum 63

ornithocephalum 63

rostratum 63
Charophyceae, 4
Chlamydobotrys 27

gracilis 11
Chlamydomonas 34, 129; al-
so 82

nivalis 34; also 13

Pa/me//a-stage 40

polypyrenoideum 34

sphagnicola 34
Chlorallantus 141

oblongus 141
Chlorangium 52

stentorinum 52
Chlorella 65, 83

conductrix 65

ellipsoidea 65

parasitica 65
Chlorellidiopsis 1 43

separalibis 1 43
Chlorobotrys 136, 143

regularis 1 36
Chlorochromonas 135

mmuta 1 35
Chlorochytrium 66; also 37,

84

Lemnoe 66; also 37
Chlorocloster 1 39

pyreniger 1 39
Chlorococcales 6, 64, 65,

80, 82, 84
Chlorococcum 42, 62, 83

humicola 42

iifusiorum 42
Chlorogonium 33
Chloromonadophyta 8, 10,

23
Chloromonads 8
Chlorophyceae 4

CHLOROPHYLL: a green
pigment of which there
are five kinds in the algae,
Chlorophyll-a occuring in
all of the algal Divisions.

Chlorophyta 4, 6, 7, 22, 25,
124, 128, 131, 136, 139

CHLOROPLAST: a body of
various shapes within the
cell containing the pig-
ments of which chloro-
phyll is the dominant one.

Chlorosaccus 142
fluidus 1 42

Chlorosarcina 37
consociata 37

Chlorothecium 133, 135
Pirottae 133

Chlorotylium 1 1 7
cataractum 1 1 7

Chodatella 79, 84

200

HOW TO KNOW THE FRESH-WATER ALGAE

Chondrocystis 1 77
Schauinslandii 177

CHROMATOPHORE: b o d y
within a cell containing
the pigments of which
some one other than
chlorophyll (green) is pre-
dominant; may be red,
yellow, yellow-green or
brown.

Chroococcaceae 178

Chroococcus 1 80
limneticus 1 80
limneticus var. distans .

180
Prescottii 1 80
turgidus 1 80

Chroomonas 1 50
Nordstedtii 1 50

Chrysamoeba 148, 156
radians 1 48

Chrysidiastrum 1 56
catenatum 1 56

Chrysocapsa 1 57
paludosa 1 57
planctonica 1 57

Chrysophyceae 144

Chrysophyta 7, 11, 22, 63,
68, 124, 128, 131, 132,
134, 135, 139, 144, 148

Chrysosphaerella 1 54
longispina 1 54

Chrysostephanosphaera 1 57
globulifera 1 57

Chrysostrella 1 46
paradoxa 1 46

CILIA: fine, hair-like exten-
sions of a cell membrane
used as organs of locomo-
tion or for feeding in the
Protozoan Class, Ciliata.

CILIATA: a Class of the
Protozoa, swimming by
means of numerous, fine,
hair-like extensions of the
cell membrane.

Citrus, trees as hosts for
algae, 1 1 5

Cladophora 120, 121; also
102

Cladophora Balls 120

Cladophoraceae 67

Class, defined 4

Closteridium 65
lunula 65

Closteriopsis 69
longissima 69

Closterium 63, 68, 70, 72;
also 65, 69

Coccomyxa 40, 44
dispar 40

Coccomyxaceae 78

Cocconeis 188
Pedi cuius 188

Coelastrum 58
cambricum 58
microporum 58

Coelosphaerium 182, 185;
also 67

Kuetzingianum 182
Naegelianum 1 82

COENOCYTIC: a plant with
multinucleate cells or cell-
like units; a multinucleate
non-cellular plant, e. g.
Vaucheria (See Fig. 199).

Coenogonium 1 09

Colacium 52, 100
arbuscula 52

Coleochaetaceae 51

Coleochaete 97, 112, 114,
122

Nitellarum 97
orbicularis 97
soluta 97

COLLAR: a thickened ring
or neck surrounding the
opening into a shell
through which a flagel-
lum projects from the in-
closed organism.

Collecting 12, 14, 15

COLONIAL MUCILAGE: a
gelatinous investment or
sheath which incloses
several to many cells.

COLONY: a group or close-
ly associated cluster of
cells, adjoined together
or merely inclosed by a
common investing muci-
lage or sheath; cells not
arranged in a linear ser-
ies to form a filament.

COLUMNAR CELLS: See
corticating cells.

Compsopogon 1 26
coeruleus 1 26

CONCENTRIC: arranged
about a common center.

CONE-SHAPED; CONICAL: a
figure circular in cross
section, broad at the base
and tapering symmetrical-
ly from base to apex.

CONFLUENT: running to-
gether or intermingling,
as mucilaginous sheaths
of plants becoming in-
termingled. Fig. 344

V \ l I

\ w

i I

i I

I)

Figure 344

CONJUGATION: sexual re-
production between cells
which become joined or
"yoked" together, the
gametes (sex cells) mov-
ing in an amoeboid fash-
ion. Fig. 34o

CONJUGATION TUBES:
tubes which are put out
by one or both cells in
sexual reproduction pro-
viding for the uniting of
gametes; see Conjugation.

CONSTRICTED: cut in or
incised, usually from two
opposite points on a cell
so that an isthmus is
formed between two parts;
indented, as are the lat-
eral walls of cells of a
filament at the cross
walls. Fig. 346

Figure 345

Figure 346

CONTRACTILE VACUOLE: a
small vacuole (cavity)
which is bounded by a
membrane that pulsates,
expanding and contract-
ing.

Copepod 2

Coronastrum 42, 51
aestivale 42

CORTEX; CORTICATING
CELLS: cells superim-
posed on the main fila-
ment or axial part of a
plant body; investing cells,
e. g., Chara, Batracho-
sperrr.um. (See Fig. 2)

Cosmarium 76; also 6, 75,
88, 89, 99
margaritatum 76
panarhense 76

Cosmocladium 46
tuberculatum 46 .

CRENULATE: wavy with
small scallops; with small
crenations.

CRESCENT: an arc of a
circle; a curved figure
tapering to horn - like
points from a wider,
cylindrical midregion. See
lunate.

CROWN CELLS: the cells
formed at the tips of the
investing elements that
are spirally twisted about
the egg in the Characeae.

Crucigenia 56; also 49
irregularis 49
rectangularis 56
tetrapedia 56

Cryptomonas 1 50
erosa 1 50

Cryptophyceae 5, 7

Cryptophyta 8, 1 1

Ctenocladus 1 1 8
circinnatus 1 1 8

CUP-SHAPED: a more or
less complete plate (as a
chloroplast) which lies just

201

HOW TO KNOW THE FRESH-WATER ALGAE

within the cell wall, open
at one side to form a
cup. Fig. 347

Figure 347

CUSHION: a pad; a thick-
ened plate.

Cyanoderrr.a bradypodis 1 3

Cyanophyta 7, 12, 139, 158,
183

Cyc/onexis 1 55
annulatus 1 55

Cyclops 52

CYLINDRICAL: a figure,
round in cross section,
elongate with parallel lat-
eral margins when seen
from the side, the ends
square or truncate. See
subcylindrical.

Cylindrocapsa 1 08

geminella var. minor 108

Cylindrocystis 71; also 72
Brebissonii 71

Cylindrospermum 1 70
ma jus 1 70
marchicum 1 70

CYST, a thick-walled rest-
ing cell or stage of an
organism.

Cystodinium 1 49
cornifax 149

Dacry/ococcops/'s 1 84

acicularis 184

-fascicularis 184
Docty/ococcus 52, 58

infusionum 52
Dactylothece 44; also 78

confluens 44
Dasyg/oea 165

amorpha 165

DAUGHTER CELLS:, cells pro-
duced directly from the
division of a primary or
parent cell; cells produced
from the same mother
cell.

DAUGHTER COLONY: a
group of cells closely ar-
ranged, having been
formed from the division
of a parent cell.

Debarya 96

Derepyxis 147
dispar 1 47

Dermatophyton, synonym of
Ulvella, 1 1 5

Desmatractum 68, 77
bipyramidatum 68

Desmidium 90; also 89

Bailey i 90; also 89

Grevillii 90
Desmids, 15, 46, 63, 69,

72, 78, 89-91
Desmonema 175

Wrangelii 175
Diachros 136, 143

simplex 1 36
Diatoms 7, 11, 12, 145, 186
Dichothrix 167

gypsophila 167
Dichotomosiphon 1 23

ruberosus 123

DICHOTOMOUS: dividing or

branched by repeated

forkings, usually into two

equal parts, or segments.
Dicranochaete 51, 67

reniformis 51
Dictyosphaerium 47; also 60

Dulchellum 47
Dirr.orphococcus 47, 60

cordatus 47

lunatus 47
Dinobryon 145, 146, 155,

156; also 2, 22

sertularia 145
Dinoflagellatae 2, 8, 11, 14,

82, 149
Diplocolon 175

Heppii 175
DISC; DISC-SHAPED: a flat

(usually circular) figure;

a circular plate.
Dispora 49

crucigenioides 49

DISTAL: the forward or an-
terior end or region as
opposed to the basal end.

Division (of the plant king-
dom) defined, 4

Docidium 7 1
Baculum 7 1
undulatum 71

DORSAL, the back or upper
surface or part as opposed
to the under or lower
(ventral) surface of a cell
or organism.

DORSIVENTRAL: referring
ro differentiation into an
upper (dorsal) and a low-
er (ventral) surface or
side.

Draparnaldia 123
glomerata 1 23

Draparnaldiopsis 123

Drying Specimens, 16

Dunaliella 36
salina 36
viridis 36

DWARF MALE: a minute
male plant (as in the
Oedogoniaceae) growing
on or near the female
sex organ (oogonium) in
a larger filament.

tchinosphaerella 78; also 79

limnetica 78
Economic Importance 1, 2
Elakatothnx 39, 42, 50;

so 78
ame r /cana
gelatinosa
viridis 39

ELLIPSOID:

al-

39
39

an ellipse, a
plane figure with curved
margins which is elongate,
the poles more sharply
rounded than the lateral
margin. Fig. 348

ECCENTRIC: arranged with-
out a common center; lo-
cated to one side of cen-
ter

Figure 348

ENCYSTED: See cyst.

ENDOPHYTE: living within
the cells or internally
among the cells of a
plant.

ENDOSPORES: non - motile
spores, indefinite in num-
ber, cut out from within
a plant cell, or (as in
Chamaesiphon) cut off
from the tip of the pri-
toplast and liberated one
by one.

ENDOZOIC: living within the
cells or among the tis-
sues of an animal.

Enteromorpha 98
intestinalis 98

Entocladia 112, 114
polymorpha 1 1 2

EPIPHYTE: living upon a
plant, sometimes living in-
ternally also.

EPIZOIC: living on or at-
tached to an animal.

Eremosphaera 8 1
viridis 8 1

Errerella 57

bornhemiensis 57

Euastropsis 36; also 55
Richteri 36

Euastrum 75, 77; also 6
pectinatum var. inevolu-

tum 75
oinnatum 75

Eudonna 29; also 26
elegans 29
unicocca 29

Euglena 25, 13 0; also 10,
23, 52

convoluta 25
elastica 25

Euglenaceae 2

Euglenophyta 7, 10, 23

EUPLANKTON: true or open-
water plankton (floating)
organisms. See plankton.

Excentrosphaera 83
viridis 83

EYE-SPOT: a granular or
complex of granules (red
or brown) sensitive to light
and related to response
to light by swimming or-
ganisms.

202

HOW TO KNOW THE FRESH-WATER ALGAE

FAA (Preservative) 16
FALSE BRANCH: a branch
formed by lateral growth
of one or both ends of a
broken filament; a branch
not formed by lateral di-
vision of cells in an un-
broken filament.
FALSE FILAMENT: an ar-
rangement of cells to form
a short or loose thread;
not forming a definite
linear series of cells.
Family (defined), 3
FIBRIL: a fine thread.
FILAMENT: a thread of
cells; one or more rows
of cells; in the blue-
green algae the thread
of cells together with a
sheath that may or may
not be present, the thread
of cells referred to as a
trichome, which see.
FISSION: cell division by
constriction not involving
nuclear division (mitosis).
FLAGELLAR VACUOLES: ca-
vities in the cytoplasm at
the anterior end of a
motile cell, at the base
of the flagella, which see.
FLAGELLUM: a relatively
coarse, whip-like organ of
locomotion, arising from
a special granule, the ble-
pharoplast, within a cell.
FLANGE: a longitudinal
bulge or wing-like vertical
extension from the sur-
face of an organism or
cell.
FLASK-LIKE: broad at the
base and abruptly nar-
rowed to a neck-like ex-
tension.
FLORIDEAN STARCH: a food
reserve produced within
the red algae (Rhodophy-
ta) different from the
starches formed by other
plants.
FOLIOSE: leaf-like; a flat
or curled, expanded thal-
lus.
Formalin (preservative), 16
Fragilaria 187; also 186
Franceia 56, 79, 84

Droescheri 56
Fridaea 121

torrenticola 121
FUCOXANTHIN: a brown
pigment predominant in
the Phaeophyta.
FUSIFORM: a figure broad-
est in the midregion and
gradually tapering to both
poles which may be acute
or bluntly rounded;
shaped like a spindle. Fig.
349

Figure 349

GAMETANGIUM: any cell,
specialized or unspecial-
ized, which produces ga-
metes (mqle or female
sex cells).
GAMETE: a sex cell; cells
which unite to produce a
fertilized egg or zygo-
spore, which see.
Gemine//o 106, 107
interrupta 1 06
mutabilis 1 06
Genicularia 72, 94; also 73

elegans 72
GENICULATE; GENICULA-
TION: bent, as a knee-
joint; bending or abrupt-
ly curved.
Genus, defined, 3
GIRDLE VIEW: see Valve.
Glaucocystis 129, 178
duplex 1 29
Nostochinearum 1 29
Glenodinium 1 53
Kulczynski 1 53
Gloeobotrys 143

limneticus 1 43
Gloeocapsa 1 80
punctata 1 80
Gloeochaete 128, 178; also
129

Wittrockiana 128
Gloeochloris 1 42

Smithiana, synonym of
Chlorosaccus fluidus, 1 42
Gloeocystis 41, 46, 48, 82,
129; also 40, 99
ampla 41
gigas 4 1
major 4 1
Gloeotaenium 61, 85

Loitelsbergerianum 61
Gloeothece 185

linearis 185
Gloeotrichia 166; also 167
echinulata 1 66
natans 166
Pisum 1 66
Glycerin, in preservative, 16,

17; in mounts, 22, 150
Glycerin Jelly, for mounts,

16, 17
GLYCOGEN: a starch-like
storage product question-
ably identified in food
granules of the Cyano-
phyta.
Golenkinia 61, 79
paucispina 6 1
radiata 6 1
Gomontia 116; also 117

Holdenii 1 1 6
Gomphonema 188 -*
Gomphosphaeria 179, 184
aponina 1 79
lacustris 1 79
Gonatozygon 73
aculeatum 73
Gonatozygonaceae 72, 73
Gongrosira 117, 119; also
118

Debaryana 1 1 7
Goniochloris 1 42

scu/pta 1 42
Gonium 26
pectorale 26

Gonyaulax 1 52
palustre 1 52

Gonyostomum 23; also 8
semen 23

GREGARIOUS: an associa-
tion; groupings of indi-
viduals not necessarily
joined together but close-
ly assembled.

GULLET: a canal leading
from the opening of fla-
gellated cells into the
reservoir in the anterior
end. (See Euglena, Fig 8.)

Gymnodinium 151
fuscum 1 5 1
palustre 151

Gymnozyga 90; also 88
moniliformis 90

GYPSUM: granules of cal-
cium sulphate which occur
in the vacuoles of some
desmids. (See Closterium,
Fig. 86.)

H

HAEMATOCHROME: a red
or orange pigment, espe-
cially in some Chloro-
phyta and Euglenophyta,
which masks the green
chlorophyll.

Haematococcus 30, 130; al-
so 22, 33
lacustris 30

Hapalosiphon 1 69
hibernicus 1 69

HARD WATER: abundantly
supplied with dissolved
minerals; with a pH above
neutral (7.0).

Herr.idinium 1 53
nasutum 1 53

Herbarium Specimens 16

HETEROCYST: an enlarged
cell in some of the fila-
mentous blue-green algae,
usually empty and differ-
ent iln shape from the
vegetative cells. Fig. 350

Figure 350

HETEROGAMETE: a gamete
(sex cell) clearly differ-
entiated in respect to
maleness or femaleness
(antherozoid and egg).

Heterokontae 1 26

HOLD-FAST CELL: a basal
cell of a filament or
thallus differentiated to
form an attaching organ.

Holopedium 1 8 1
irregulare 1 8 1

HORIZONTAL GROWTH:
growth more or less at
right angles to outward-
ly or upwardly projecting
filaments or parts; usual-
ly growth parallel with a
substrate to which a plant
is attached.

203

HOW TO KNOW THE FRESH-WATER ALGAE

Hormidiopsis 1 05
ellipsoideum 1 05

Hormidium 107; also 104-
106
Klebsii 107

Hormotila 99
mucigena 99

Hot Springs 1 3

H-SHAPED SECTIONS: seg-
ments of filaments or ter-
minal cells of filaments
which result from separa-
tion of cells, one from
the other, at the midre-
gion rather than at the
cross walls, the cell wall
being composed of two
sections which adjoin and
overlap midway between
the end walls. (See Figs.
172, 212); also in a chlo-
roplast shape where there
are 2 broad sections ly-
ing along the side walls
and connected by a nar-
row cross band. Fig. 351

Figure 351

Hyalobryon 1 46

mucicola 1 46
Hyalotheca 90; also 88, 135

dissiliens 90

mucosa 90
Hydra 65
Hydrocoleum 1 64

homeotrichum 1 64

oligotrichum 1 64
Hydrodictyon 54

reticulatum 54
Hydrurus 1 44

foetidus 1 44
Hye//a 176

iontana 1 76

INCISED; MEDIAN INCI-
SION: cut in; with a
narrow cut from the mar-
gin. Fig. 352

i/

'

Figure 352

Indian Turnip 66

INFOLDED: as in cross walls
of a filamentous alga
which are not smooth,
even membranes but have
folds extending back into
the cavity of the cell.
Desmidium and certain

species of Spirogyra have
this type of wall; repli-
cate.

INTERCALARY: arranged in
the same series, as spores
or heterocysts which oc-
cur in series with vegeta-
tive cells rather than be-
ing terminal or lateral.

INTERNODE: the space or
section of a filament or
rhallus extending between
branch - bearing or en-
larged portions (nodes).

INTERSTICES: openings or
spaces between adjoined
cells; openings in the
mucilage which incloses
colonial algae.

INTESTINIFORM: a thallus
in the form of a tube,
often crinkled, sometimes
branched.

INVAGINATION: concavity;
a depression from an oth-
erwise smooth or plane
surface.

IODINE TEST: application of
a weak solution of iodine
(Lugol's) to determine
presence of starch; starch-
iodide, which is formed
when iodine is applied to
cells of the Chlorophyta,
appears as a blue-black
substance.

ISODIAMETRICAL: a figure
with all planes having an
equal diameter or nearly
so.

ISOGAMETE: a sex cell
which shows no detect-
able differentiation in re-
spect to maleness or fe-
maleness.

JOINT: point or plane where
two cells or elements ad-
join.

Jack-in-the-pulpit, see Ari-
saema

K

KELP: common name for

the larger brown sea

weeds.
Kentrosphaera 84

Bristolae 84
Kirchneriella 49, 65; also 53

lunaris 49

obesa var. major 49

Lagerheimia 79, 84; also 56

longiseta 79

quadriseta 79
Lagynion 147

reductum 147

triangularis var. pyramida-
tum 147
LAMELLA; LAMELLATE:

with layers; with plates

lying against one another.

LAMINARIN: a polysaccha-
ride carbohydrate used as
food storage in Phaeo-
phyta.

LAMINATE: plate-like; lay-
ered.

LATERAL CONJUGATION:
reproduction involving the
formation of a connect-
ing tube around the end
wall of two adjacent cells
in the same filament so
that contents of the cell
may fuse to form a zygo-
spore.

Lemanea 124
annulata 124

Lemna 12, 37, 66
trisulca 12, 66

Lepocinclis 25
acuta 25
glabra fa. minor 25

Leptosira 117; also 22
Mediciana 1 1 7

LEUCOSIN: a whitish food
reserve characteristic of
many of the Chrysophyta,
especially the Heterokon-
tae; gives a metallic lus-
tre to cell contents.

Leuvenia 137
natans 1 37

LICHEN: a duplex plant
thallus formed by a fun-
gus and an alga living in
close association, 80, 109.

Lime (Marl Deposits) 21

LINEAR SERIES: cells or
units arranged in a single
row.

Lobomonas 33
rostrata 33

LOBULE: a small lobe; a
secondary division of a
lobe.

LONGITUDINAL FURROW: a
groove in the dinoflagel-
late cell which extends
parallel with the long
axis.

LORICA: a shell-like struc-
ture of varying shapes
which houses an organism,
has an opening through
which organs of locomo-
tion are extended. (See
Trachelomonas, Fig. 5.)
Fig. 353

Figure 353

LUNATE: crescent - shaped,
as of the new moon.

Lyngbya 159, 162
Birgei 1 59
contorta 1 59

204

HOW TO KNOW THE FRESH-WATER ALGAE

M

Macrocystis 2
Magnolia 115
Malleochloris 67; also 100

sessilis 67
Mallomonas 147

acaroides 1 47

caudata 1 47

pseudocoronata 1 47
Mangrove 1 26
Mannitol 9
Mare's Eggs 173
Marssoniella 184

elegans 184
MEDIAN INCISION: See in-
cision.
Melosira 186; also 187

granulata 1 86
Meridion 187

circular e 187
Mer/ngosphaera 1 40

sp/nasa 1 40
Merismopedia 179; also 181

convo/uta 179

e/egans var. major 179

glauca 179
Mesotaeniaceae 73
Mesotaen/um 44, 74

Grey// 44

macrococcum 44
METABOLIC: plastic, chang-
ing shape in motion as in

many Euglena.
METABOLISM: referring to

the physiological activities

within a living cell.
Micractinium 57

pusillum 57

quadrisetum 57
Micrasterias 74, 89; also 6

americana var. Boldtii 74

ioliacea 74

radiata 74
M/crochaete 170, 174; also

173

diplosiphon 1 70

robusta 1 70
Microcoleus 1 64

/acustr/s 1 64

vaginatus 1 64

MICROCRUSTACEAN: cope-
pods, water fleas, Clado-
cera, etc., microscopic
members of the Class
Crustacea.

Microcystis 181, 182
aeruginosa 1 8 1
flos-aquae 1 8 1

MICROFAUNA: microscopic
animals; see Microcrusta-
cea.

MICRON: a unit of microsco-
pical measurement; one
1/1000 of a millimeter,
determined by using a
micrometer in the eye-
piece of the microscope
which has been calibrated
with a standard stage mi-
crometer. Expressed by
the symbol,

Microspora 109; also 103,
131

floccosa 1 09
Loefgrenii 1 09
Willeana 109

Microthamnion 120
Kuetzingianum 1 20
strictissimum 1 20

M/schococcus 1 30, 1 42
confervicola 1 30

Monallantus 1 38
brevicylindrus 1 38

MONAXIAL: with one axis;
with a single row of pri-
mary cells in a thallus.

MONILIFORM: arranged like
a string if beads; bead-
like. Fig. 354

Figure 354

Monocilia 1 3 1
flavescens 1 3 1
viridis 1 3 1

Monostroma 97; also 98
latissimum 97

MOTHER CELL: the cell
which by mitosis or by
internal division gives rise
to other cells (usually
spores).

Mougeotia 94, 96, 116; also
3

elegantula 94
genuflexa 94

Mougeotiopsis 96
calospora 96

Mounting 6

MULTIAXIAL: with more
than one axis or more
than one longitudinal
strand in a thallus.

MULTINUCLEATE: with
many nuclei; see Coenocy-
tic.

MULTISERIATE: cells ar-
ranged in more than one
row; a filament two or
more cells in diameter.

Myrmecia 81
aquatica 81

Myxophyceae 22

N

Nannochloris 78, 85

bacillaris 78
Navicula 188; also" 187
Nephrocytium 50, 61

Agardhianum 50

ecdysiscepanum 50

limneticum 50

lunatum 50

obesum 50
Netrium 73

digitus 73
Nitella 21; also 12, 20, 97

f/ex/7/s 21

tenuissima 2 1
NODE: a position on a fila-
ment or thallus from

which branches or lateral

organs develop, usually

enlarged or swollen; a

joint in a thallus.
NODOSE, with regular swell-
ings or nodes about a

longitudinal axis.
Nodularia 172

spumigena 172
NODULE, a small swelling;

a tubercle or button-like

knob.
Nostoc 173; also 158, 185

amplissimum 173

commune 173

linckia 173

pruniforme 173
Nostochopsis 1 68

lobatus 1 68

OBLATE, slightly
sphere almost
Fig. 355

flattened
globular.

Figure 355

OBLONG, a curved figure,
elongate with the ends
broadly rounded but more
sharply curved than the
lateral margins. Fig. 356

Figure 356

OBOVATE, an ovate figure,
broader at the anterior
end than at the posterior.
Fig. 357

Figure 357

Oedocladium 111; also 102

Hazenii 1 1 1
Oedogoniaceae 102
Oedogonium 102; also 103,

122

crispum 1 02

Westii 102

205

HOW TO KNOW THE FRESH-WATER ALGAE

OBLATE-SPHEROID, a figure

which is a flattened

sphere; an almost globular

figure flattened on one

side. (See Fig. 355)
Ochrorr.onas, Synonym for

Chlorochromonas, 135
Oncobyrsa 1 77

rivularis 1 77
Onychonema 88

filiforme 88

laeve var. latum 88
Oocardium 99

stratum 99
Oocystaceae 1 29
Oocystis 62, 85; also 6, 36,

37

Borgei 62

Eremosphaeria 62
OOGONIUM, a female sex

organ, usually an enlarged

cell; an egg case.
OOSPORE, a thick-walled

resting spore formed from

a fertilized egg.
OPAQUE, not permitting the

transmission of light.
Ophiocytium 134, 138, 140,

142; also 139

cochleare 1 34

desertum var. minor 1 34

gracilipes 1 34

parvulum 1 34
Ophrydium 65
Order, defined 3
Oscillatoria 161; also 157,

158, 159, 163

rubescens 1 6 1

splendida 1 6 1
Oscillatoriaceae 158
Ourococcus 64, 69

bicaudatus 64
OVAL, an elongate, curved

figure with convex margins

and with ends broadly and

symmetrically curved but

more sharply so than the

lateral margins. Fig. 358

Figure 358

OVOID, shaped like an egg;
a curved figure broader at
one end than at the other
Fig. 359

Pachycladon 85
umbrinus 85

Palmella 38, 41 ; also 40
miniata 38
mucosa 38

Palmellaceae 99

Palmella Stage of Chlamy-
domonas 40

Palmellococcus 82, 85
miniatus 82

Palmodictyon 43, 100, 110
varium 43
viride 43

Pandorina 28; also 26
morum 28

PARAMYLUM, a solid,
starch-like storage product
in the Euglenophyta.

Paranema 23

PARASITIC, living on or in
another organism at the
expense of the host; often
pathogenic.

PARIETAL, along the wall;
arranged at the circum-
ference; marginal as op-
posed to central or axial
in location. Fig. 360

Figure 359

Figure 360

Pascheriella 27; also 29
tetras 27

PEAR-SHAPED, a figure
which is elongate and
ovate, wider at one end
than at the other, usually
distinctly narrowed in the
midregion.

PECTIN; a gelatinous carbo-
hydrate deposited in the
cell or in the cell wall of
many algae.

Pectodictyon 43
cubicum 43

PECTOSE, See Pectin

Pediastrum 55, 56; also 36
biradiatum var. emargina-
tum 55
Boryanum 55
obtusum 55
simplex 55
tetras 55

PEDICEL: a small, basal
stalk.

PELLICLE, the outer mem-
branous covering as in the
Euglenophyta; a skin.

Penium 72

margaritaceum 72

PENNALES, a subclass of the
Diatomaceae in which the
cells are bilaterally sym-

metrical and in which wall
decorations are bilateral
in arrangement from a
longitudinal axis, 186.

PERFORATE, with openings;
with pores.

PERIDININ, a brown pigment
characteristic of the Dino-
flagellatae.

Peridinium 152; also 153
wisconsinense 1 52

PERIPHERY, the outer boun-
dary; the surrounding out-
er part.

PERIPLAST, see Pellicle.

Perone 1 33
dimorpha 1 33

Peromelia 135, 142
Hyalothecae 135

Phacotus 32; also 33
lenticularis 32

Phacus 24; also 25
curvicauda 24
triqueter 24

Phaeophyta 2, 9, 11

Phaeosphaera 1 56
perforata 1 56

Phaeothamnion 1 44
confervicola 1 44

Phormidium 163, 164
amoiguum 163
favosum 163
inundatum 1 63

PHOTOSYNTHESIS, physiolo-
gical process by which
plants with chlorophyll
manufacture c a r b o h y-
drates in the presence of
light.

PHYCOCYANIN, a blue pig-
ment found in the Cyano-
phyta and the Rhodophy-
ta.

PHYCOERYTHRIN, a red pig-
ment found in the Rho-
dophyta and in some Cy-
anophyta.

PHYCOPYRRIN, a red or red-
dish-brown, water - soluble
pigment in the chromato-
phores of the Dinoflagel-
latae.

Phyllosiphon, 66, 123; also
13
Arisarii 66

Phylum, defined, 2

Phymatodocis 91
Nordstedtiana 91

PIGMENTATION; PIGMENTS,
colored substances, either
localized in special bodies
(plastids) within the cell,
or in solution within the
cytoplasm.

PIGMENT - SPOT, see Eye-
spot

Pithophora 118, 121
Mooreana 1 1 8
Oedogonia 1 1 8

PLACODERM DESMIDS, re-
ferring to those desmids
which have the cell wall
composed of two sections
that are adjoined in the
midregion of the cell
where there often is a
constriction so that "semi-
cells" are formed.

206

HOW TO KNOW THE FRESH-WATER ALGAE

PLANE (END WALLS),
smooth, not folded walls;
opposite of replicate. Fig.
361

D^^U

Figure 361

PLANKTON: organisms drift-
ing in the water, or if
swimming, not able to
move against currents.

Plankton Net 14

Planktosphaeria 48, 62
gelatinosa 48

PLASTID, a body or organ-
elle of the celle, either
containing pigments or in
some cases colorless.

PLATE, sections, polygonal
in shape, composing the
rell wall of some Dino-
flagellate (the thecate or
armored dinoflagellates).
Fig. 362

POLYGONAL, many sided.

POLYHEDRAL, a figure with
more than four sides.

Porphyridium 1 30
cruentum 1 30

Porphyrosiphon 1 62
Notarisii 1 62

POSTERIOR, toward the rear;
the end opposite the for-
ward or anterior end of a
cell or of an organism.

Prasinocladus 1 00
lubricus 100

Prasiola, 98; also 92
crispa 98

Preserving; Preserving Fluids
16 17

PROCESS, an extension of a
cell, or of a cell wall, or
of a thallus; a horn, arm,
or abrupt protrusion from
a plane surface. Fig. 363

Figure 362

Platydorina 26

caudatum 26
Platymonas 31

elliptica 3 1
Plectonema 161

Wo//ei 161
Pleodorina 30, also 29

californica 30

illinoisensis 30
Pleurocapsa 1 77

minor 177
Pleurococcus 53, 62, 83

vulgaris 53
Pleurodiscus 94

purpureus 94
Pleurogaster 139, 140

lunaris 1 39
Pleurotaenium 71; also 72

nodosum 7 1

trabecula 7 1
POLAR; POLE, referring to

the two opposite ends of

a cell or an organism,

or to differentiate points

in a circular cell; the ends

of an axis.
Polvblepharides 35

fragariiformis 35
Polyedriopsis 86, 87

quadrispina 86

spinulosa 86

PSEUDOPODIUM, meaning a
false foot; locomotory or-
gan formed by lobe-like
extension of the proto-
plasm, found in some
Chrysophyta and in the
Sarcodina Protozoa.

Pseudotetraedron 1 37
neglectum 1 37

Pseudoulvella 1 1 5
americana 1 1 5

PSEUDOVACUOLE, meaning
a false vacuole; a pocket
in the cytoplasm of many
blue-green algae which
contains gas or mucilage,
is light-refractive. (See
Microcystis, Fig. 318.)

Pteromonas .33
aculeata 33

PUNCTAE, minute, pin-point
pores within the cell wall;
minute pits either extend-
ing completely through
the wall or not. Fig. 365

' "«• • • * • • J*« L w^

Figure 363

Protococcus 53, 62, 83; also
104
viridis 53

Protoderma 1 1 4
viride 1 1 4

PROTONEMA, the filament-
ous stage in the develop-
ment of moss plants.

PROTOPLAST, the living part
of a cell; the cell mem-
brane and its contents,
usually inclosed by a cell
wall of dead material.

Protozoa 2, 12, 23

PSAMMON, the organisms
inhabiting the soil (espe-
cially sand) above the
high water level of lake
or river beaches.

Pseudochaete 1 1 2
gracilis 1 1 2

PSEUDOCILIA, meaning false
cilia; flagella-like struc-
tures not used for locomo-
tion.

PSEUDOP ARENCHYMA-
TOUS, a false cushion; a
pillow-like mound of cells
(usually attached) which
actually is a compact of
short, often branched fila-
ments. Fig. 364

Figure 365

PYRAMIDAL; PYRAMIDATE,
in the shape of a pyra-
mid; a pointed, 3-sided
figure with a broad base.
Fig. 366

Figure 366

10

Pyramimonas 35; also
tetrarhynchus 35

PYRENOID, a protein body
around which starch or
paramylum collects in a
cell, usually buried in a
chloroplast but sometimes
free within the cytoplasm.

PYRIFORM, see Pear-shaped
Fig. 367

Figure 364

Figure 367
Pyrrhophyta 8, 11, 82

207

HOW TO KNOW THE FRESH-WATER ALGAE

QUADRATE, four-sided; with
a general outline showing
four sides

Quadrigula 50
Chodatii 50

Raaborskia 149
bicornis 1 49

RADIATE, extending out-
ward in several planes
from a common center;
extending in one plane
in several directions from
a common point.

Radiofilum 106
conjunctivum 1 06
flavescens 1 06

Ragweed 66

RAPHE, a longitudinal canal
within the wall of diatoms
belonging to the Pennales,
forming a median line on
one or both sides of the
diatom shell.

RECTANGULAR, a figure
with four right angles.

RECTILINEAR, arranged in
straight rows in two di-
rections

Red Algae, see Rhodophyta

Red Snow, see Snow

RENIFORM, kidney - shaped;
bean-shaped. Fig. 368

Figure 368

REPLICATE, infolded; fold-
ed back as in the cross
walls of some Spirogyra;
not a straight or plane
cross wall. Fig. 369

Figure 369

RESERVOIR, cavity in the
anterior end of flagellated
cells from which the or-
gans of locomotion arise

RETICULATE, netted; ar-
ranged to form a net-
work; with openings. Fig.
370

Figure 370

Rhabdoderma 185
linear e 185

Rhizochrysis 148, 156
limnetica 1 48

Rhizoclonium 102, 116, 121;
also 103

hieroglyphicum 102
Hookeri 1 02

RHIZOID; RHIZOIDAL, root-
like; a downward project-
ing root-like branch or
cell, usually without regu-
larity.

RHIZOPODIAL, irregularly
branched, root-like exten-
sions of protoplasm used
for locomotion.

Rhodochytrium 66, also 22
spilanthidis 66

Rhododendron ] 1 5

Rhodophyta 8, 1 1, 22 110
124, 126, 127, 129.

Ricciocarpus 1 2
natons 1 2

Rivulana 167; also 166

Rivulariaceae 160

Rotifer 12

Roya 73
obtuso 73

SACCATE, like o sac; bal-
loon-like cell or colony of
cells, or plant body. Fig.
371

Figure 371

SACCODERM DESMID, false
desmids; cells which have
plane, unpitted walls all
in one piece. See Placo-
derm Desmid.

Sacconema 166
rupestre 166

SARCINA ARRANGEMENT,
cells arranged in the form
of a cube.

SCALARIFORM, ladder-like;
sexual reproduction by
conjugations tubes formed
between cells of two fila-
ments forming a ladder-
like figure.

Scenedesmus 57, 58; also
6, 36

bijuga var. alternans 57
incrassatulus var. mono-

nae 57
opoliensis 57
quadricauda 57

Schizochlamys 45; also 136
gelatinosa 45

Schizogoniaceae; Schizogoni-
ales, 92, 98

Schizogonium 92; also 98
crenulatum 92
murale 92

Schizomeris 101 , 110
Leibleinii 101

Schizothrix 165
tinctoria 165

Schroederio 64, 69
ancora 64
Judayi 64
setigera 64

Scotiella 84; also 14, 33
nivalis 84

SCROBICULATE; SCROBICU-
LATION, with saucer-like
depressions in a plane sur-
face (cell wall), sometimes
deep. Fig. 372

"5o O O O 6o3~o-v
o ooo 0o °o

Figure 372

Scytonema 174
Archangelii 1 74

Scytonemataceae 161, 175

Sea Weed 1 1

Sea Wrack 2

Selenastrum 53, 65
gracile 53

SEMICELL, a cell-half, as in
the Placoderm desmids in
which the cell has two
parts that are miror im-
ages of one another, the
two parts often connected
by a narrow isthmus.

SEPTUM, a cross-partition,
cross wall or a membrane
complete or incomplete
through the short diam-
eter of a cell, sometimes
parallel with the long
axis.

SERRATE, toothed; jagged.

SETA, a hair, usually aris-
ing from within a cell
wall; or a hair-like ex-
tension formed by taper-
ing of a filament of cells
to a fine point. Fig. 373

Figure 373

SHEATH
ly of
firm;
colony

a covering, usual-
mucilage, soft or
the covering of a
of cells or an en-
velope about one or more
filaments of cells.

208

HOW TO KNOW THE FRESH-WATER ALGAE

SICKLE - SHAPED, acutely
curved; cresecnt - shaped
but curved more sharply
than an arc of a circle.
Fig. 374

Figure 374

SIPHON; SIPHONOUS, a

tube; a thallus without

cross partitions.
Sirogonium 95

sticticum 95
SKEIN, a web-like expanse;

a thin membranous

growth.
S'oth 13 _ nA

Snow Algae 13, 14, 34, 84,

129
Sorastrum 60

americanum 60

spinulosum 60
Species defined 3
Sphaerellopsis 34

iluviatilis 34
Sphaerocystis 48

Schroeteri 48
Sphaeroplea 1 03

annulina 1 03
Sphaerozosma 89

excavata 89
Sphagnum 15, 70, 90, 110,

1 33
SPHERICAL, not quite sper-

ical.
SPICULE, a scale or needle

in the wall of cells or as

a decoration on a cell

wall.

SPINDLE-SHAPED, see Fusi-
form.

SPINE, a sharply - pointed
projection from the cell
wall.

Spirogyra, 95, 116; also 3,
6, 72, 94, 101
aequinoctialis 95
elongata 6
rhizobrachiales 95

Spirotaenia 72
condensate 72

Spirulina 158; also 159
laxissima 1 58
princeps 1 58
subsalsa 1 58

Spondylomorum 27
quaternarium 27

Spondylosium 89
pulchrum 89

Sponge 65

SPORANGIUM, a cell (some-
times an unspecialized
vegetative cell) which
gives rise to spores; the
case which forms about
zygospores in the Zygne-
matales (Conjugales).

Starch 7, 8, 1 1

STARCH-TEST, See Iodine
Test

STAR-SHAPED, see Stellate
Staurastrum 75, 76
cornutum 75
rotula 75
STELLATE, with radiating
projections from a com-
mon center; star-like.
Stephanodiscus 1 86 ; also
187

niagaroe 1 86
Stephanoptera 35

gracilis 35
Stephanosphaera 29

pluvialis 29
Stichococcus 104

bacillaris 1 04
Stigeoclonium 113, 123; al-
so 108, 112
flagelliferum 1 1 3
Stigonema 169
muscicola 1 69
oce//atum 169
turfaceum 1 69
Stinging Cells 23
STIPE. a stalk, usually

slender.
Stipitococcus 1 34
urceolatus 1 34
vasiformis 1 34
Stone-wort 1, 21
STRATIFIED, with layers
Stylosphaeridium 67

stipitatum 67
SUB-APICAL, slightly below
the apex or below the an-
terior end.
SUBCYLINDRICAL, a figure
which is elongate with
lateral margins that are
parallel for most of their
length. See Cylindrical.
SUBFLAGELLAR, located at
the base of or just below
the point of origin of
flagella.
SUBQUADRANGULAR, not
quite square or with four
rounded angles.
SUBSPHERICAL, not quite

spherical. See Oblate.
SULCUS, groove or depres-
sion in cells of Dinoflagel-
latae. (See Peridinium,
Fig. 258)
Surirella 1 88

splendida 1 88
SUTURE, a groove between
plates, as in some Dino-
flagellatae; a cleft-like
crack or line in the spore
wall as in some zygo-
spores.
Symploca 1 63

muscorum 1 63
Synechococcus 1 83 ->

aeruginosas 183
Synechocystis 1 78

aquatilis 178
Synura 154; also 2
Adamsii 1 54
uvella 1 54

TEGUMENT, a skin; a firm

outer covering.
TEST, a shell or covering ex-
ternal to the cell itself.
See Lorica.
Tetmemorus 69

laevis 69
Tetradesmus 59
Smithii 59
w/sconsinense 59
Tetradinium 1 49
javanicum 1 49
simplex 1 49
Jetraedron 87; also 6, 86,
149

asymmetricum 87
limneticum 87
lobulatum var. crassum 87
regulare var. biiurcatum

87
regulare var. granulatum
87
TETRAGONAL, with 4 angles
which are arranged in two
opposite pairs.
Tetragoniella 141

gigas 1 4 1
TETRAHEDRON, see Tetra-
gonal
Tetrallantos 49, 59

Lagerheimii 49
Tetrapedia 183

Reinschiana 183
Tetraspora 38, 44, 45, 100;
also 39, 42, 156
cy lindrica 38
gelatinosa 38
Tetrasporaceae 1 28
Tetrasporales 64, 67, 82, 99
Tetrastrum 55; also 56

heterocanthum 55
THALLUS, a plant body
which is not differentia-
ated into root, stem and
leaf organs; a frond; the
algal plant.
Thea 1 1 5

THECA; THECATE, a firm
outer wall, a shell, some-
times with plates as in
the Dinoflagellatae.
Thorea 1 25

ramossisima 1 25
Tolypella 20

intricata 20
Tolypothrix 174

distorta 174
TOW; TOW SAMPLE, collect-
ing with a plankton net
by drawing it through the
water.
Trachelomonas 24; also 22

granulosa 24
Trachychloron 1 4 1
biconnicum 141
TRANSVERSE FURROW, a
groove extending lateral
around a cell as in the
Dinoflagellatae. Fig. 375

Jabellaria 1 87

fenestrata 1 87
Tea 115

Figure 375

209

HOW TO KNOW THE FRESH-WATER ALGAE

TRAPEZIFORM; TRAPEZOID,
a figure which has two
parallel sides; shaped
somewhat like a trape-
zoid. Fig. 376

Figure 376

Trebouxia 80
Cladoniae 80

Trentepohlia 109, 116, 119;
also 10, 13
aurea 1 09
lolithus 109

Treubaria 87
crassispina 87

Tribonema 131; also 132
bombycinum 1 3 1
bombicinum var. tenue

131
utriculosum 131

TRICHOCYST, organelle
which is capable of throw-
ing out stinging fibrils of
mucilage. (See Gonyosto-
mum, Fig. 4.)

Trichodesmium 162, 163
erythraceum 1 62
lacustris 1 62

TRICHOGYNE, a slender ex-
tended neck on the fe-
male sex organ (carpo-
gonium) of the Rhodophy-
ta.

TRICHOME, a thread; the
series of cells in the Cy-
anophyta exclusive of a
sheath which may be pres-
ent; a fine hair-like ex-
tension.

Triploceras 70
gracile 70

Trochiscia 80
granulata 80
obtusa 80
reticularis 80

TRUE BRANCH, a branch
formed by means of later-
al division of cells in the
main filament of a plant.

TRUNCATE, cut off abruptly
at the tip; flat at the
end as opposed to being
rounded or pointed. Fig.
377

Figure 377

TUBERCLE, a button - like
knob or protuberance.

TUBULAR; TUBULAR T HAL-
LUS, a thread-like growth
without cross walls; a
plant body in the form
of a tube.

TUMID, swollen or convex
on the sides. Fig. 378

Figure 378

Tuomeya 1 26
fluviatilis 1 26

Turtle 13, 19

TYCHOPLANKTON, the
plankton of waters near
shore; organisms floating
and entangled among
weeds and in algal mats,
not in the open water of
a lake or stream

U

also 101

Ulothrix 107, 1 08;

aequalis 1 07

cylindricum 1 07

zonata 1 07
Ulotrichales 53
Ulvella 1 1 5

involens 1 1 5
UNDULATE, regularly
UNILATERAL, on one
UNISERIATE,

in a single

tiseriate.
Urococcus 82

insignis 82
Uroglenopsis

americana
Uronema 1 08

elongatum 1 08
UTRICLE, a sac-like or tub-
ular sheath, usually a firm

mucilaginous covering. Fig.

379

cells
row.

155
155

wavy.

side,
arranged
See Mul-

Figure 379
Utricularia 15, 51

VALVE, one of two parts
of a diatom cell wall;
valve view, when the cell
is seen from the top or
bottom; girdle view, when
the cell is seen from the
side which thus shows the
overlapping of the two
valves.

Vaucheria 1 24
geminata 1 24
sessilis 1 24

VEGETATIVE, referring to a
non - reproductive stage,
activity, or cell, as op-
posed to activities and
stages involved in repro-
duction, especially sexual
reproduction.

VENTRAL, the under or low-
er side or surface of an
organism or cell.

VERMIFORM, long, narrow
and crooked in shape,
worm-shaped.

VERRUCA, a warty projec-
tion; a protrusion which
bears knobs or spines.
Fig. 380.

y^^

Figure 380

VERRUCOSE, roughened;
with irregular thickenings
on the surface. Fig. 381

VESICLE, a sac or balloon-
like cell or thallus.
Volvocaceae 26
Volvocales 27, 36, 84
Volvox 28; also 29, 30 155
tertius 28

W

WATER BLOOM, a profuse
growth of planktonic al-
gae which cloud or color
the water, often forming
floating scums.

Water Net (Hydrodictyon)
54

Westella 60
botryoides 60

WHORL, several
branches or leaves
ing at one level
around an axis.

Wislouchiella 32
planctonica 32

VVollea 171
saccata 1 7 1

parts,
aris-
from

210

HOW TO KNOW THE FRESH-WATER ALGAE

Xanthidium 77

cristatum var. uncinatum
11

Xanthophyceae 124, 128,
134

XANTHOPHYLL, a yellow
pigment of several kinds
associated with chloro-
phyll, C H O .

46 56 2

Xenococcus 176
Schousbei 1 76

Yellow-brown Algae 6

Zoochlorella 65, 83

conductrix 65

parasitica 65
ZOOSPORE, an animal-like

spore equipped with fla-

gella and usually with an

eye-spot.

Zygnema 93; also 3, 92
pectinatum 93

Zygnemataceae 3

Zygnematales 95

Zygnemopsis 92
decussata 92
desmidioides 92

Zygogonium 93
ericetorum 93

ZYGOSPORE, spore resulting
from the union of gam-
etes (sex cells); a resting
stage.

211

FRESH-WATER ALGAE