CHARLES PAUL ALEXANDER

U.S. COMMISSION OF FISH. AND FISHERIES,
GEORGE M. BOWERS, Commissioner.

ee : ‘ ~~ CONTRIBUTIONS TO THE BIOLOGY OF THE GREAT LAKES.

THE PLANKTON ALG-E OP LAKE ERIE,

WITH SPECIAL REFERENCE TO THE CHLOROPHYCE-.

JULIA. WwW. SNow,

Instructor 1m Botany, Sintth College, Northampton, Mass.

~

Extracted from U.S. Fish Commission Bulletin for 1902. Pages 369 to 394, Plates I to IV;

eB

WASHINGTON:
GOVERNMENT PRINTING OFFICE.
1903.

Ameer
Paee

CHARLES PAUL ALEXANDER

U.S. COMMISSION OF FISH AND FISHERIES,
GEORGE M. BOWERS, Commissioner.

CONTRIBUTIONS TO THE BIOLOGY OF THE GREAT LAKES,

Pi PLANKTON ALGA OF LAKE ERIE.

WITH SPECIAL REFERENCE TO THE CHLOROPHYCEA.
“BY

JULIA W. SNOW,

Lnstructor in Botany, Smith College, Northampton, Mass. °

CSS ce

Extracted from U, §, Fish Commission Bulletin for 1902. Pages 369 to 394, Plates I to IV.

WASHINGTON:
GOVERNMENT PRINTING OFFICKEH.
MOOR.

2

CONTRIBUTIONS TO .THE BIOLOGY OF THE GREAT LAKES.

THE PLANKTON ALGA: OF LAKE ERIE, WITH SPECIAL REFERENCE TO
ME CHEOK Omen Ay:

By JULIA W. SNOW,
Instructor in Botany, Smith College, Northampton, Mass.

F. C. B. 1902—24 369

CONTRIBUTIONS TO THE BIOLOGY OF THE GREAT LAKES.

THE PLANKTON ALGA? OF LAKE ERIE, WITH SPECIAL REFERENCE TO
. TE sCnLONORnY CRA:

By JULIA W. SNOW,
Instructor in Botany, Smith College, Northampton, Mass.

INTRODUCTION.

The unicellular algee, which in themselves show most interesting characteristics
in their structure and life history, come to have a double significance when consid-
ered in connection with their environment. Investigation shows the presence of an
intimate connection and interdependence between them and their surroundings.
While they depend upon substances in the water for nutrition, they in turn prob-
ably perform a valuable function, the same that has been proved by Bokorny 794
and Strohmeyer ’97, in the case of some higher alge, that of purifying the water,
reducing the amount of bacterial growth accompanying decay, and rendering the
medium fit for higher life. Their value also as a food supply to the aquatic fauna
is well known. In any biological study of a body of water the alge must therefore
receive attention, and should be considered with reference to their environment
rather than as independent unrelated entities.

A study of this kind should be continued for a number of years, for aside from
the desirability of repeated observations, it is necessary on account of variations in
the flora from year to year. Certain species may be abundant each year, but others
are periodic in their appearance, being found only at intervals of three or four years;
and forms, more or less polymorphic, have been known to appear almost exclusively
in one condition one year and in another condition the next, so that their identity
has not been known until their life history has been traced. Such variations must
be due to variations in environment, so that before these phenomena can be under-
stood the environment must be known and its influence determined.

In the natural state, the elements in environment are so numerous and so
connected that to know definitely which of these produce a certain effect on an
organism is impossible. This must be ascertained under artificial conditions and
experimentation must be resorted to for this purpose. Under these circumstances
the environment may be altered, certain of its elements may be eliminated and the
effect of others studied, so that after repeated trials we may arrive at more definite
knowledge of the life principles of these organisms than would be possible in the
native state. When the relation to environment is definitely known, then we may
go still further and, by changing this environment, exert a certain control over these

371

372 BULLETIN OF THE UNITED STATES FISH COMMISSION.

organisms, causing them at will to reproduce, or to assume any stage in their
development which we may desire.

At present great confusion exists in the nomenclature of these lower vegetable
organisms. Many, in certain stages of their development, can not be distinguished
from one another, and even some polymorphie filamentous algee have often been
confused with unicellular forms, as they may assume a unicellular condition in
which even a skilled observer is unable to distinguish them with certainty from true
unicellular plants. The entire life history should therefore be traced, and although
there may be stages in the development of different ones which can not be readily
distinguished, a broader knowledge must aid in recognition.

To determine accurately the life history of a species, observation should be
made from pure cultures. The need of this has been pointed out by Klebs 796,
Artari 792 and Senn °99, and has often been suggested by the inaccurate work of
a number of investigators, in which many species have been confused. If one
start with a single cell or a small cluster of cells, all of which are known to be the
same, and from these procure an unlimited supply of absolutely pure material, then
one can assert with certitude that whatever developments occur they are character-
istic of that species, whereas if the material be not pure one is easily misled as to
the connection of different forms. But even a pure culture under one set of condi-
tions is not sufficient. Material should be subjected to all possible conditions which
might ever occur in nature, and the effect of these conditions studied in all phases
of development. When this is done we may venture to classify the organism, and
then many phenomena not now understood will-probably be explained.

In the present study, which was continued during the summer of 1898, 1899,
and 1900 at Put-in Bay, Lake Erie, and at Ann Arbor, Mich., in 1900, the work
has been largely preparatory, and has been confined to comparatively few of the
numerous forms present. The first summer was devoted principally to becoming
acquainted with the forms found in Lake Erie, and in experimenting with culture
media, that pure cultures of the different forms might be obtained and the condi-
tions governing development be determined. It was soon found that although alge
existed side by side in the water of the lake, the conditions which determined their
growth were not the same—that the favorable conditions for development must be
determined for each genus, and often for each species individually. Comparatively
few would live at all in the media which are so generally used for more hardy forms
found in stagnant pools. After determining the favorable media for some of the
most common forms in the plankton, the following summers were devoted to tracing
their life history and studying such biological facts as could be determined.

As the amount of work to be done was so great, it was thought best to limit
investigation to some special group, and as the Chlorophycew are more easily main-
tained in culture and are more varied in their development, requiring more constant
observation, they were taken first. All species to which special attention is given
in this paper, unless a statement to the contrary is made, were taken from the
plankton, and an abundance of pure material was obtained by cultivation. Cultures
were made in the ordinary Stender dishes, and parallel with these were also
continued hanging drop cultures, where the development of the same individuals
could be observed from day to day and no step be overlooked.

Aside from tracing the development of a number of the members of this group,

ro

PLANKTON ALG OF LAKE ERIE. : 373

a partial list is added of the alge occurring in the plankton, though this is by no
means complete, as comparatively little time was given to the determination of the
Diatoms. The material was merely preserved for future examination. The
determination of the Desmids was mainly left to Mr. A. J. Pieters, who has given a
list of this family. (Pieters 01.) A number of the Cyanophycece also, which are
common in the plankton, have not been determined. These are minute gelatinous
forms occurring as flocculent masses in the water, and though the structure of the
cells is constant, the form of the colony is more or less variable, depending
apparently on the age of the colony and the kind and amount of nutritive sub-
stanees in the water. To make an accurate list of these would require careful
comparison and a more perfect knowledge of their life conditions than we now have.
Undoubtedly many of them are undescribed species. Though the list of Chloro-
phycee here given is fuller than that of other classes, it is by no means complete.
Some unrecognized forms were met with where attempts at cultivation failed, due
to inappropriate culture conditions, and as a result classification could not be made.

In the examination of fresh plankton material, the more conspicuous forms were
easily detected, but there were always a number of minute forms, such as Chlorella,
Chlorosphera, and Chlamydomonas, which easily escaped notice, or, if observed,
they appeared as single green cells which could not be identified. That these might
be taken account of, and not be altogether overlooked, large cultures were started
from the fresh plankton, and in these cultures developed many such forms which
had escaped observation in the examination of the fresh material. Some of these
were isolated from all other forms of alge and their development studied. It is
believed, however, that farther study in this line will give many additional species
and many interesting biological facts, for as yet but few of these larger cultures
have been thoroughly examined and the species determined.

For the names of species, where a detailed study is not given, the determination
is based on the simple descriptions of other authors. The list is given, however,
only as a temporary guide to the forms present, for it is believed that new methods
of investigation, when applied to the development of even some of the best recog-
nized genera, will change the nomenclature considerably. Some forms which have
been classed together may prove to be distinct species, and possibly others which
show variation should be combined to form one species.

In the physiological work done on these forms, by far the greatest amount of
attention has been given to the subject of nutrition and culture media. Tempera-
ture is of less importance, for relatively great variations do not seem to affect them.
The water in the natural condition never reaches a temperature so high as to kill
them, and low temperature—even freezing, at least in sone cases—does not end their
existence, but seems to affect them mainly in reducing their rate of increase. The
degree of light, too, in which they can live would seem to vary largely, as they are
often found at considerable depth, as well as at the surface. The belief of many
recent investigators that algee with chromatophores may make use of both organic
and inorganic substances in their nutrition, is supported by the experiments of
Artari 701 and Knorrich ’01, both of whom found that the alge used in experi-
mentation thrived much better when organic substances were present in addition to
the inorganic. Artari even found that at least certain forms could live and remain
green in total darkness. .

It has been the experience of the writer that great variation exists among

374 BULLETIN OF THE UNITED STATES FISH COMMISSION.

different algee on this point and that the kind of substance and the amount best
suited to development must be determined for every alga selected for culture.
While some grow more luxuriantly in a purely inorganic solution, others, among
which are the unicellular blue-green algze, seem to prefer a solution where at most
but a trace of mineral matter is present. The culture medium most favorable in a
large number of cases was a decoction made from the organic matter of the plank-
ton. ‘Thisseemed especially favorable if large quantities of Anabeena flos-aque were
present. This observation that the organic matter of the water could be used by the
algze has suggested a possible explanation of the great increase of alge at certain
seasons, causing the ‘‘ water bloom.” This phenomenon has been observed by the
writer but three times, but at each time it was known that an unusual amount of
dead organic matter was in the water of that vicinity. At one time the matter was
in the form of numerous small dead fish floating on the water; at another time a
quantity of refuse had been emptied into the bay where the water bloom was noticed;
and a third time large areas of the surface of the water were covered with the skins
of Ephemera which are shed before the insect reaches the imago state. Such phe-
nomena as these can be explained only experimentally, and it is along these-lines of
increase and source of nutrition that further investigation should be carried.

THE STRUCTURE AND LIFE HISTORY OF CERTAIN PLANKTON ALG£Z.

Chlamydomonas gracilis Snow, new species.

This species of Chlamydomonas (fig. 1) in its most vigorous and normal motile condition is
cylindrical, ovoid or ellipsoidal in shape, rounded at the posterior end and bluntly pointed at the
anterior end. Length 10.5 to 13 4; breadth 5 to 6.5 4. In the nonmotile condition the cells are
ovoid or spherical, and often motile individuals of the same shape are noticed, with a diameter of 9
to 10.5 «. The chloroplast and entire contents are sometimes withdrawn from the membrane either
at the anterior or posterior end. When at the anterior end the two protoplasmic flagella can be seen
to be continuous with the protoplasm within. The flagella are somewhat longer than the cell.

The single hollow chloroplast lines the membrane throughout, except for a very small area
just at the anterior end, at which point two pulsating vacuoles can be seen. The color is a dull
bluish-green, rather than a vivid green. Oil is always present. The pyrenoid is in the extreme
posterior end of the cell. The pigment spot is a conspicuous dull-red disk, and is often situated
as far back as midway between the two ends or even farther. The nucleus occupies a position
between the center and the anterior end of the cell. After division the cells are liberated by the
enveloping membrane becoming dissolved at one point, through which the new individuals escape,
leaving the empty membrane behind.

This species, like most species of Chlamydomonas, grew and reproduced readily in a 0.2 to 0.4
per cent Knop’s solution, and this culture medium was used to trace the life history of the species.

On transferring material from Knop’s solution to water, individuals were formed which were
taken to be the gametes, though only in one instance was indication of copulation noticed (fig. 1, 4).
These were in all respects like the ordinary motile form, except that they were smaller, ovoid in
shape, and had no membrane (fig. 1,3). Though the species resembled Chlamydomonas debaryana
Goros., it is much smaller and more cylindrical in shape than that species.

This species was found 23 miles north of Kelley Island,in Lake Erie. It is by no means widely
distributed in the water of the lake.

Chlamydomonas communis Snow, new species.

This species in the motile stage resembles closely the preceding species, but after cultivating
the two forms in pure cultures side by side for over two years, and finding characteristics which are
distinguishing and constant, they have been separated into two species. The size and shape of the
two are almost identical, the shape being oval or ellipsoidal and pointed at the anterior end (fig. 11).

PLANKTON ALG OF LAKE ERIRF. 315

The dimensions are 10.5 to 13 “ long and 6.5 to 8 “ broad. The color is a brighter and yellower
green than that of the preceding species; the pyrenoid, instead of being at the extreme posterior
end of the cell is near the center, and the pigment spot is an inconspicuous elongated strip of dull
red which can rarely be distinguished, except when viewed at the side. In all other respects the
structure of this species resembles that of the preceding. The division is longitudinal. Chlamydo-
monas communis, though in general appearance greatly resembling Chlamydomonas media Klebs,
is smaller, the largest cells being only about half as large as the largest of that species. The mode
of division also in the two species is so different that the two could not be classified together.

This species was found in many collections taken at the western end of Lake Erie.

Chlamydomonas globosa Snow, new species.

In the natural condition in the plankton of Lake Erie this species exists abundantly, but in a
form not easily recognized as a Chlamydomonas. In appearance it resembles Plewrococeus regu-
laris Artari, consisting of one or more clusters of spherical cells, more or less separated from each
other, and all imbedded and held in place by a thick, gelatinous covering. When first placed in
culture the gelatinous envelope disappears, the cells become isolated and the normal appearance of
a Chlamydomonas is assumed; but when division occurs the alga takes again the cluster form as
found in the plankton.

In the motile form the cells are spherical or slightly ellipsoidal, with a diameter of 5 to 7.8 w.
No anterior beak is present. There are two flagella, as long or slightly longer than the cell, and
a small inconspicuous pigment spot at the side, about half way between equator and cilia (fig. ur).

The chloroplast extends to the extreme anterior end of the protoplast, and is much thickened
at the posterior end, in which portion the pyrenoid lies. The pyrenoid is enveloped by a thick
layer of starch. Only a single pulsating vacuole can be distinguished at the anterior end, but this
is unusually large in size. Several globules of oil are present in the anterior portion of the cell.
Often the cell contents are withdrawn from the membrane, either at the anterior end, the posterior
end, or at all points. Gametes were not found.

After division the cells are liberated by the cell wall becoming gelatinous. In 0.2 per cent
Knop’s solution, where division took place normally and rapidly, the cells existed in clusters of
four, which resembled in every respect some of the cell compounds found in the plankton. This
species of Chlamydomonas was cultivated for a period of two years, and during this time no
variation was noticed.

Scenedesmus bijugatus var. flexuosus Lemm.

The form under consideration is identical with Scenedesmus bijugatus var. flecuosus described
by Lemmerman ’99, except that in a ccenobium 32 cells seem to occur more frequently than 16
(fig. 1v,1). Both numbers frequently appear in the plankton of Lake Erie, however, and the
two forms are undoubtedly the same. This variety was cultivated by the author for about a year
under a large number of conditions, and as some points were observed, not noted in Lemmerman’s
description, they are given here.

It was first thought from its general resemblance to S. bijugatus that it might be this species
which had assumed a greater development due to unobstructed light and the inexhaustible supply
of oxygen. carbon dioxide, and nutritive substances which are constantly supplied by the ever-
moving water of the lake, but cultivation of the species for some months, during which many
generations were traced, proved that the great number of cells was characteristic for the organism,
and that when placed under the artificial conditions, where the supply of air and nutrition were not
so constantly renewed as in the lake, it did not necessarily revert to the usual form of S. bijugatus
with 8 cells. It is true that. under special conditions, where the vitality was low, it sometimes
produced an 8-celled ccenobium, but in the same culture where 8 cells were found ccenobia of 16
or 32 cells were also found. The ccenobia of 8 or 16 cells produced again ccenobia of 32 cells, so
that it would seem that the larger number of cells was normal, rather than abnormal.

The greatest diameter of the cells of a mature coenobium is 20.8 4, while the shortest is 8.9 u.
A young coenobium of 32 cells measured 160 in length, while an older one measured 364 “. The
great length of one of these individuals strongly suggests a filamentous alga. The shape of the
cells in young ccenobia is cylindrical, with slightly rounded ends. In older individuals which are

376 BULLETIN OF THE UNITED STATES FISH COMMISSION.

passing into a resting condition the ends become more rounded and the shape more ellipsoidal. In
the mature resting stage the cells are spherical (fig. Iv, 2).

The membrane is perfectly smooth without processes or markings of any kind. The composi-
tion of the membrane is cellulose, turning blue when treated with iodine and sulphuric acid. In
the younger individuals the membrane is comparatively thin, but when the cell passes into a rest-
ing condition the membrane becomes very much thickened, is 2.5 to 3.25 4 in diameter, and two,
three, or sometimes four layers are distinguishable. The thick inner layers are also of cellulose,
while the outermost layer becomes to a greater or less degree cutinized. As the cells pass into a
resting stage and become spherical in shape, the surface of contact between two adjoining cells
becomes less and less, and finally they break away from each other and exist singly.

The chloroplast, under natural conditions, is a thin, homogeneous layer, irregularly interrupted
at the center, and forming a lining to the membrane. At one side near this point a large pyrenoid
is present. Under cultivation, in most media, the chloroplast assumes a granular appearance on
the surface and the perforations are obscured. Later a large amount of oil is developed which is
readily dissolved in absolute alcohol. As the cell passes into a resting condition this oil gradually
assumes an orange color. On account of the ease with which the cells pass into a resting condition
the normal condition of the chloroplast can with difficulty be maintained under cultivation.

The nucleus is small and les near the pyrenoid, sometimes on one side, sometimes on the other.
Staining with hematoxylin brings out the presence of several large vacuoles in the cell cavity.

In its relations to external conditions this variety seems in many ways to deviate from most
other alge. Ina numberof solutions, found generally to be favorable for algal culture, this variety
simply passed into a resting condition. The only solution tried which really proved to be favorable
was a solution of decaying Anabena flos-aque, which occurred at times in great quantities on the
surface of the lake. In this the development seemed normal.~ In an organic solution (decaying
peas) and in 0.2 per cent Knop’s solution the color became green and healthy, but no reproduction
occurred, at least for many weeks. <A solution from the organic material of the plankton
proved favorable to reproduction, but old and young coenobia alike soon became filled with orange-
colored oil, passing into a resting condition, and remained in this condition until the nutrition of
the medium was finally exhausted, or until they were transferred to.a fresh and favorable solution.

Of the inorganic solutions, Sachs’s, Knop’s, Oelmann’s and Knop’s solution without calcium, .
Sachs’s solution was the only one that was at all favorable. Here reproduction occurred readily,
and the cells assumed a normal appearance, but even in this solution, after a time, the coenobia
gradually passed into a resting condition.

Staurogenia apiculata Lemm.

This species, which is very generally, though not universally, found in the plankton of Lake
Erie, is undoubtedly that described by Lemmerman 798 as Stawrogenia apiculata. His figure
and measurements agree quite closely with those of the Lake Erie species, though his description
leaves us in some doubt in regard to details.

In Lake Erie this alga may occur either as individual coenobia, composed of 4 ces lying in
one plane (fig. v, 4,5), or these coenobia may be united into large, more or less irregular rectangular
plates of cells, measuring 50 to 150 ~ on a side (fig. v, 1).

The 4 cells of the ccenobium are either lemon-shaped or oval, and are arranged to form a
rectangle with a diamond-shaped space at the center. Of all the species of the Canobie, this
is apparently the most constant in regard to the number of cells. In other members of this
tribe the number of cells of any daughter individual depends very largely upon external conditions
and the vitality of the parent ccenobium, but of the many thousand ccenobia of this species examined
under widely varying conditions, only one individual showed any deviation as to number of cells.
In this case division was incomplete and but 3 cells were formed instead of 4, though four pyrenoids
were present. E

The large plate-like structures which are found in the tow, and which also occur in cultures,
arise from the daughter coenobia remaining after liberation in the position in which they are
formed (fig. v, 1), being held in place by a colorless, gelatinous substance which surrounds each
individual. As each of the 4 cells gives rise to a daughter ccenobium of 4 cells, all of which lie in
the same plane, a plate of 16 cells is formed, and as each of these again produces a coenobium,
a compound ccenobium of 64 cells is produced. This process continues, but the plate-like struc-

PLANKTON ALG OF LAKE ERIE. BT

ture soon becomes more or less broken and distorted, as is seen in the material from the plankton,
and the irregularity increases as reproduction continues. As the gelatinous substance which
holds these together is invisible without reagents, one receives the impression that each plate-like
mass is a coenobium or individual, whereas in reality it is made up of many.

Under normal conditions of growth the cells of this species are ovoid or lemon-shaped, with the
membrane projecting into a very short and almost obscure wart at one or both ends of the cell
(fig. v, 4,5). The typical shape is evidently that of a lemon which is more or less unsymmetrical
with reference to its long axis. But in the ccenobia where two cells are in contact their opposed
ends often become more or less flattened. The projecting portions of the membrane are then often
not formed, and the cells are quite distinctly ovoid, the broader portions of the adjoining cells
turned toward each other. The mature cells measure 5.2 to 8 long and 3.25 to 5.2 /« broad, while
in young ccenobia they are 5 to 5.8 « long and 3.25 to 4 broad.

The membrane is very thin and consists of cellulose as shown when treated with iodine and
sulphuric acid. Surrounding the membrane and enveloping the whole ccenobium or compound
ccenobium is the homogeneous gelatinous substance which unites the separate coenobia. This is
apparently excreted from the cells and is not a dissolved portion of the membrane, as the mem-
branes of one or more preceding generations are sharply defined and lie embedded in this substance
(fig. v,1). The ways in which this responds to different stains are various. Fuchsin-iodine
green neither stains the gelatinous substance nor is capable of penetrating it. It therefore leaves
the cell contents uncolored. Hematoxylin, fuchsin, and safranin stain the cell contents, but not
the gelatinous envelope; the latter, however, takes a deep color with gentian violet. The structure
is best brought out by tannate vesuyine which stains it brown. With this stain single ccenobia
show but a single layer of this substance, often thicker than the diameter of the cells themselves,
though varying somewhat in amount. In the large compound ccenobia several layers are made
visible, each successive outer layer being less dense than the adjoining inner layer. These different
layers are the gelatinous envelopes developed during the different generations and retained from
' one generation to the next. The inner denser layer is sharply outlined from the others and is 3 to
3.5 4 thick. With the tannate vesuvine fine radiating lines are brought to view at right angles to
the surface of the cell, and undoubtedly indicate a prismatic structure (fig. v, 2) such as described
by Klebs °86 for Zygnema. The second or next outer layer shows no such striations, but is quite
definitely outlined, while the third and outermost visible layer is more or less indistinct and
gradually vanishes into the surrounding medium.

The chloroplast is thin, parietal, and forms a close lining to the membrane. In some young
coenobia, on the side of the cell next to the central space, there was seen to be an opening through
the chromataphore, but in mature specimens no trace of an opening could be detected. Lying
imbedded in the chloroplast is a single, relatively large pyrenoid surrounded by a thick layer of
starch. The position of the pyrenoid in the cell is in no wise constant, as sometimes it lies nearer
one end of the cell and sometimes nearer the other. Its position also in reference to the nucleus
is not constant; the latter, however, occupies different positions in the cell according to the age.

In young ccenobia the nucleus invariably occupies a position near the wall adjoining the cen-
tral space (fig. v, 6a), while in older individuals it moves toward the center or near to one end of
the cell. The minuteness of the nucleus renders a detailed study difficult, but material stained
with hematoxylin showed strands of protoplasm radiating from it, and in one case a nucleolus
was plainly visible (fig. v, 8). In the same material also a stained network appeared throughout
the cell and was undoubtedly due to the arrangement of the protoplasm and vacuoles. Small
globules of oil were always present, and occasionally larger globules. This oil became darkened
by osmic acid and was dissolved in 10 per cent potassium hydrate. It was not dissolved in absolute
alechol, which would show the oil to be of a fatty rather than an ethereal nature.

The new individual arises from the successive bipartition of the contents of any cell of the
ceenobium. The first division is a transverse one (fig. v, 4). The second division, which occurs
in each of the products of the first division, is at right angles to the first and in the same plane in
the two products, so that the elements are arranged in the form of a rectangle while still within
the mother membrane. The division of the different contents of the cell is not simultaneous, as
the chromataphore is divided before the pyrenoid, and judging from their relative position in the
cell at this time, both of these divide before the nucleus. The four daughter nuclei occupy a
position near the point of contact of the four chromataphores (fig. v. 4a), while the pyrenoids lie

318 BULLETIN OF THE UNITED STATES FISH COMMISSION.

toward the opposite end of the daughter cell (fig. v, 4). The nuclei retain this position in the cell
for some time after the cells are liberated (fig. v,6). Before liberation each cell becomes invested
with a membrane.

The daughter coenobium is set free by the membrane of the mother cell becoming ruptured
from the middle of the base to the apex, so that one longitudinal half is loosened and thrown
back like a lid, thus setting free the daughter individuals (fig. v,7). Under conditions where but
little gelatinous substance is present and only single ccenobia are produced, many such empty
membranes are found in the surrounding medium. Where the gelatinous substance is in great
abundance, and large plates of cells are formed, these remnants of membranes for two or more
generations may be found clinging to the sides of the cells.

Physiology.—This species of Stawrogeniais greatly affected by the kind of substances available
for nutrition. Cultures were made in a large number of different solutions—Knop’s solution, sugar
solution, decoctions of mixed vegetable and animal matter found in the plankton, decoctions of
pure vegetable matter, and decoctions of earth. Other solutions were also used which will be
referred to later. In most cases cultures were made in a number of different concentrations of the
same solution, so that amount of substance, as well as kind, was taken into consideration. For
rapidity of increase the organic solutions seemed to be of far more importance to the species than
the inorganic, and the solutions found most favorable to this were the decoctions of organic matter
from the plankton, though a solution from decaying peas was also favorable. In fresh cultures in
these solutions the plates usually consisted of sixty-four cells (fig. v, 1), one-half usually being
folded back upon the other, but in the older cultures, where the material had increased greatly,
the plates were small, consisting in a large number of cases of sixteen cells (fig. V, 2).

Knop’s solution, which is a favorable medium for a large number of alge, did not prove
favorable to either reproduction or development in this species. In cultures of 0.4 per cent, 0.1
per cent, and 0.05 per cent of this solution, very little increase took place, the color was pale and the
regularity of the coenobia was lost, while, owing to the absence of gelatinous substance, the large
masses were never formed. In 0.1 per cent and 0.05 per cent growth was more abundant than in
the 0.4 per cent. The cells showed no regularity of arrangement, however, and no trace of
gelatinous substance could be detected even when treated with tannate vesuvine (fig. v, 3). In
the decoctions of earth development was normal, increase was rapid, and the general condition was
vigorous. In a 2 per cent sugar solution the species lived but a short time. In cultures where
nutrition had become exhausted the cells assumed a dull rust color, due to the presence of oil.
This probably was a resting stage, though all attempts to resuscitate it after it had been dried in
this condition failed; when not dry, however, the green color soon returned if fresh nutrient
solution was added.

As this species did not flourish in Knop’s solution the question arose as to what element in the
compound was detrimental to the alga and prevented development. It was thought that it might
be the large amount of calcium in Knop’s solution which produced this effect, and to determine
this point Knop’s solution was then made without calcium, and a solution without calcium used
by Oelmann in the cultivation of sphagnum was tried. Cultures were made in various concen-
trations of both these solutions with the following results: In a 0.4 per cent Oelmann’s solution
development was far more natural than under any other artifical conditions, the group of cells
being much larger than in other cultures. The same appearance, though to a less extent, was
found in other concentrations—0.1 per cent and 0.05 per cent of the same solution and also in 0.5
per cent and 0.25 per cent of Knop’s solution without calcium. Apparently, then, calcium inter-
feres with development, and in nature the organism probably would not find a habitat in water
containing much of this element, but would seek a soft water rather than a hard. The number of
clusters which were formed in these cultures without calcium was few in comparison to the
number in organic solutions and the cells were a trifle smaller. The direct cause of the develop-
ment being higher where the individuals are fewest was not determined in this case, but it seems
to be true of the other algze as well as of this.

Fusola viridis Snow, new genus and new species.

In the natural condition, as found in a stagnant pond in Middle Bass Island, in Lake Erie, the
cells of this species were single, fusiform in shape, and sometimes slightly sigmoid (fig. v1, 3). They
vary from 27 to 39 in length and 8.5 to 21 in width. A medium size is 28.5 “ long and 8 broad.

PLANKTON ALG OF LAKE ERIE. 379

A distinguishing character is the gelatinous covering, usually about 6.5 to 8 /« thick, surrounding
each cell. This is excreted from the cell and is of such a consistence as to be plainly visible
under the microscope, but shows no laminated structure. In mature cells no further structure is
visible in the gelatinous substance; but in rather young individuals, if cells be stained with tannate
vesuvine, and sometimes without staining, two portions of the ruptured mother membrane are
seen lying imbedded in this gelatinous substance (fig. v1, 4).

The membrane of the cell is composed of cellulose , which shows the blue color with iodine
and sulphuric acid. The gelatinous envelope remains unaltered in appearance with these
reagents. The chloroplast occupies the larger portion of the cell, leaving near the center only a
relatively small space, which in direct view appears as a lighter circle. In this lies the nucleus.
A large pyrenoid is prominent, lying also near the center of the cell. Small globules of oil occur
and become darkened by osmic acid. In old cultures the cell assumes something of a brownish
color, which may represent a resting stage, but when such a brownish cell was allowed to dry it
could not be induced to grow again.

The reproduction takes place by a single transverse division of the contents of the mother cell
(fig. vi, 1. 2). The two parts thus formed gradually elongate in opposite directions from the
point where division took place, one slipping by the other in the process (fig. v1, 3, 4) and both
becoming invested with a membrane. As the gelatinous material is excreted from the cells they
become gradually separated from each other, the surrounding membrane is diagonally ruptured,
and the cells are set free. The division is rapidly repeated so that the appearance is asif 4, 8, or
16 cells originated at once from a single cell, but in the present study in no case were more than
two cells seen to originate at one time from a parent individual.

The shape of the cells and the formation of colonies is largely controlled by the nutrient
medium in which the alga grows. A large number of cultures were made in different solutions,
and it was found that 0.05 per cent Knop’s solution most nearly reproduced the species in the form
in which it was first found. In a weak decoction of earth and in an infusion of Anabaena flos-
aque the cells assumed a much longer and more slender form, while on agar mixed with 0.4 per
cent Knop’s solution all resemblance to the original form was lost, the cells becoming perfectly
spherical, with dark contents, and a wide, gelatinous envelope. In a solution containing organic
matter from the plankton, also in the decoction of earth, gelatinous masses were formed as large
as a pea, while in 0.05 per cent Knop’s solution the cells usually existed either singly or in smaller
clusters of 4 to 16 cells. After some months these cultures appeared as a vivid green jelly, due to
the great increase in the number of cells.

In some of the general characteristics this species resembles those species of Oocystis, where
the cells lie imbedded in a gelatinous matrix, but the fusiform shape, the greater density of the
gelatinous envelope. and the structure of the chloroplast would all indicate that it can not be
classified with Oocystis.

Oocystis borgei Snow, new species.

In frequency of appearance and the form in which it occurred this species showed great varia-
tion during the three summers when observations were made. In 1898 it was not noted at all in
the plankton, while in 1899 it was the most abundant of all of the Chlorophycece and appeared
in large complexes of many cells grouped into twos, fours, or eights, and all imbedded in a homo-
geneous, transparent, gelatinous substance. In a very few cases colonies of two cells were noted.
In 1900 these large gelatinous masses were never observed, but the small colonies of two or four
cells. such as described by Borge (‘00) occurred frequently. From the large’ gelatinous masses
pure cultures were easily obtained. The cells measure 13 “4 long and 9 se broad, and the shape is
ellipsoidal or slightly fusiform (fig. vu, 1, 2,3).

The membrane is a thin layer enveloping the contents. Outside of this is a thick, gelatinous,
covering which unites the cells into colonies, and varies in thickness from one-half to twice the
diameter of the cell (fig. vu, 4,5). The membrane consists of cellulose, taking a blue color with
iodine and sulphuric acid. Cells in the natural condition and young cells in culture showed the
membrane to be of the same thickness at all points, but some older cells in culture, though not
all, showed the membrane to be somewhat thickened at the ends. This thickening, however, did
not take the nature of a wart or projection, such as has been noted in other species. The outer

380 BULLETIN OF THE UNITED STATES FISH COMMISSION.

gelatinous envelope becomes stained with haematoxylin and also with tannate vesuvine. With
the latter it is homogeneous and shows no prismatic structure characteristic for such coverings in
many similar forms of alge. Two layers can often be detected, however, the inner one the more
dense. The outer one probably belongs to the preceding generation (fig. vu, 4).

There is but a single, vivid green, homogeneous. parietal chloroplast, through which there is
an opening at one side or near one end. From this opening the chloroplast gradually increases in
thickness toward the opposite side, where it incloses a large pyrenoid (fig. vil, 1, 2). The
central portion of the pyrenoid shows a crystalline character, and is surrounded by a thick starch
envelope. The single spherical or elongated nucleus lies near the center (fig. vir, 1a). With
hematoxylin a network throughout the cell is brought to view, and is probably due to the arrange-
ment of protoplasm and vacuoles. Oil is found in greater or less quantity in all cells. This oil is
turned brown by osmic acid and becomes dissolved in absolute alcohol.

Reproduction occurs by means of bipartition or repeated bipartition of the cell contents, so
that two, four, or eight cells are formed from one individual. The first division is a transverse
one (fig. vil, 3a); then, if the process continues, the next divisions, dividing the products of
the first, take place at right angles to the first division and at right angles to each other (fig. V1,
3b). Each part then becomes invested with a membrane and the outer gelatinous substance
begins to be excreted by the cells before they are set free from the mother cell. The enveloping
mother membrane becomes much distended, probably by means of the gelatinous substance (fig.
vu, 4), until finally it becomes ruptured at one point and the two, four, or eight cells are set free,
leaving the remnant of the old cell wall clinging to the outer surface of the gelatinous covering
(fig. vit, 3, 5). Though in young individuals there is but a single chromatophore, this very
soon becomes divided into two or four, long before the division of the cells occurs, so that in a
culture the great majority of cells contain four chromatophores, and it was first thought that four
was the normal number. Preceding the division of the chlorophyl body occurs the division of the
pyrenoid. The division of the nucleus does not occur until just before the formation of the
daughter cells and long after the division of the chloroplast.

Physiology.—Though in the natural conditions the cells are usually found united into larger
or smaller complexes, the aggregated form of growth is by no means necessary to existence and is
characteristic only under certain conditions, for under the various environments to which the alga
was submitted in artificial culture, it was found that either the isolated or aggregated condition of
the cells could be produced at will. Cultures were made in various media, such as different
concentrations of Knop’s solution, decoctions of earth, and solutions containing animal and
vegetable matter taken in the tow from the lake and stagnant ponds. Of the various solutions
used the organic solutions seemed best to reproduce the aggregated form as it is found in the
plankton, but even here the masses were not quite as large as those in the natural condition,
although the appearance of the individual cell was perfect (fig. vi1, 4). The concentration of the
organic solution had a marked effect in producing the isolated or aggregated condition in the
development. The exact amount of substance in solution was not determined, but it was found
that in the solution which was taken as a standard the cells were all grouped in colonies, and
several of these were united into compound colonies. In the same solution, but of one-half the
standard concentration, and even in the above solution after the concentration had become
reduced by the growth and increase of the algae, only isolated cells were formed, which were
distributed throughout the liquid instead of resting on the bottom of the culture glass, as occurred
in most cultures. Each individual cell was surrounded by a gelatinous covering one-half to
twice the diameter of the cell in thickness, but these were not held together by a common
envelope (fig. vu, 5). The vigor of the culture, however, seemed just as great as where the
families were formed. It is probable that the greater amount of water present in proportion to
the organic matter reduced the consistency of the gelatinous substance, and the connection
between the cells was broken.

Knop’s solution of different concentrations did not seem to be favorable to development, for in
no case was the appearance normal. Cells were usually isolated and a great amount of oil was
developed in the contents. In 1 per cent and 0.4 per cent increase was slight, while in 0.1 per cent
and in 0.05 per cent, notwithstanding a very large amount of oil being present (fig. vi1, 5), increase
was rapid. In the decoction of earth growth was abundant and normal, except for the presence
of a large amount of oil.

PLANKTON ALGA OF LAKE ERIE. 381

This species certainly resembles closely the Oocystis lacustris described by Chodat ’97, but
after cultivating the two forms, both of which occur in Lake Erie, and obtaining an abundance of
pure material of both, each was found to show certain characteristic differences which separate
them into different species. The most striking of these was the protruding point at the ends of the
cell of Oocystis lacustris, while in the other species, if any thickening was noticeable at the poles,
it did not project in the form of a wart, but was a gradual thickening of the membrane. Another
difference, which was constant, was the longer and more slender shape of Oocystis lacustris.

From the figure given by Borge, 1900, of a form occurring in Sweden, it would seem that the
species in question must be the same, though the dimensions are slightly smaller than those given
by Borge. Inrecognition of Borge having first figured the species it has been called Oocystis borgei.

Chodatella citriformis Snow, new species.

This new species is distinguished from other species of this genus by the shape of the cell, there
being a short, obtuse elongation at either end, and at the base of these are arranged the whorls of
spines which characterize the genus (fig. vil, 1, 2, 3).

The length of the cells varies from 8 to 10 “. The spines are very delicate, often 33 to 36 u
long and but 0.5 broad at the base. In different individuals six, seven, eight, and nine spines
were found. It was not thought by the author, however, that these represented different species,
although some authors seem to distinguish different species by the number of spines. Unfor-
tunately, large cultures of this species were not obtained; and although cells were observed through
several generations in hanging drop cultures, it could not be determined whether or not the num-
ber of spines was constant in the descendants of a single individual, for as soon as an individual
was confined ina hanging drop, the spines became gradually indistinct, finally disappearing, and
the daughter individuals possessed either no spines or very rudimentary ones. Apparently the
spines were of a gelatinous nature. In the test for cellulose with iodine and sulphuric acid they
quickly disappeared when the acid was added. The reaction for cellulose was obtained in the
membrane.

The chlorophy] is contained in a single parietal chloroplast, leaving the opposite side colorless.
A pyrenoid lies embedded in the chloroplast.

The reproduction occurs by the cell contents becoming divided into two, four, and sometimes
eight parts. Each becomes invested with a membrane, and forms a daughter individual (fig. vim, 3).
Though the actual process of liberation of the cells was not witnessed by the author, due to insuf-
ficient material, it was inferred that they were set free by the rupturing of the membrane, as
membranes were found which were undoubtedly the empty mother membranes of this species. _

Chodatella citriformis was found in surface tow and at a depth of about 10 meters, near North
Bass Island, in Lake Erie.

Pleurococecus regularis Artari.

One of the most conspicuous and common of all the plankton algz is a form determined by
the writer as Pleurococcus regularis Artari (fig. 1x, 1). It consists of cell complexes composed
usually of 4, 8, 16, or 32 clusters of cells, more or less separated from each other and embedded in
a transparent, gelatinous substance (a). Each cluster in turn is composed of 4, 8, 16, or 32 cells,
which may be in contact with each other or may be separated from’ each other and held in place
by the same gelatinous material. Without doubt it is these complexes which Senn ’99 regards as
stages in the development of Celastrum microporum Naeg., and Chodat as stages of Celastrum
spherium Naeg. The striking resemblances of these complexes to Ceelastrum was noted by the
writer when the alga was first seen in the plankton. The view held by Chodat as to the identity
of the two forms was then accepted and the difference in appearance was regarded simply as dif-
ferent phases of the same form, due to different conditions. It was noted, however, that side by
side in the large plankton cultures, as well as in the fresh collections, both forms were found. The
one corresponding to Celastrum consisted of single, isolated coenobia composed of many closely
arranged cells with very little surrounding gelatinous substance. The other form consisted of
many clusters, widely separated from each other and embedded in a common gelatinous matrix.
The individual cells also, as well as the ccenobia, were more or less separated from each other
according to age. With a view to determining definitely whether these were the same species in
diferent stages or distinct forms, each was isolated and placed in culture under the same condi-

382 BULLETIN OF THE UNITED STATES FISH COMMISSION.

tions. The difficulty attending the cultivation of the Plewrococcus-like form was very great, and it
was not until after a very large number of attempts had been made that vigorous cultures were
obtained from which conclusions could be drawn with any degree of certainty. All ordinary solu-
tions, so commonly used in the cultivation of algee, failed as culture media. In 0.2 to 0.4 per cent
Knop’s solution the form simply assumed a yellowish color and passed into a resting condition.
In Knop’s solution without calcium it remained green for at least six weeks, but showed no indica-
tion of reproduction. Organic solutions of various compositions and concentrations proved more
favorable to its existence, but even in these not more than three generations could usually be
obtained in any culture. The only solution tried that seemed really favorable was from a quantity
of decaying Anabcena flos-aque. The chemical composition of this solution and the degree of
concentration were not determined, but in it reproduction took place rapidly, and, as far as could
be determined, normally. This solution proved equally favorable for Ceelastrum. Pure cultures
were then made of each of the forms and placed in conditions as nearly alike as possible.

In the course of four weeks an abundance of material of both forms was obtained. These cul-
tures were then repeated several times, and the results agreed each time. Even externally a differ-
ence in the cultures could be detected. The Celastrum form showed as a very thin green covering
on the bottom of the culture glass, while in the other culture a thick cloudy layer, 3 to 4 mm. deep,
covered the bottom. A minute examination showed a still more marked difference, and one which
was identical with the two forms from which the cultures were made. The thick layer on the
bottom of the Plewrococcus culture was composed of the floating loose compound clusters embedded
in jelly exactly as in the plankton, except perhaps that the arrangement of the cells was less regular
(fig. x, 2-4). Unless reproduction had just occurred all the cells were more or less separated
from one another, sometimes widely so, but all were held in place by the surrounding jelly. Ina
fresh Celastrum culture, where there were many hundreds of ccenobia, but one instance was
noticed where any separation of a cell from a coenobium occurred. Each of the other coenobia was
complete and distinct, without any connection with the other coenobia in the culture (fig. rx, 5). »
In old cultures the disintegration of the coenobia was more frequent, but in no case after disintegra-
tion had occurred were the individual cells connected by a surrounding gelatinous substance. There
is, as Senn (1898) has stated, a relatively thin gelatinous envelope to the cells, but after the cells have
become appreciably separated from one another this envelope no longer connects them. In no case
did Celastruwm microporum form compound clusters. Asa result of these experiments, it seems
evident to the writer that the two forms are distinct species and can not be united.

Artari (°92), in his description of Plewrococcus regularis, says nothing about the presence of a
gelatinous envelope, but from his figures it is evidently present, as the cells, though loosely
arranged, are held in place by some substance not shown. The gelatinous envelope of a cluster,
when taken from the plankton, as well as of those in the artificial culture, is homogeneous, but
somewhat denser near the cells. When treated with tannate vesuvin the jelly is colored brown,
but no prismatic radiations from the cell are shown, as in Stawrogenia apiculata Lemm. The
thickness of the envelope seems to vary somewhat with age, Leing in young individuals less in
diameter and denser in consistency than in older compounds (fig. rx, 2, 3). When distilled water
is added the substance becomes at least partially dissolved.

The membrane is thin and consists of cellulose, turning blue when iodine and sulphuric acid
are added. he chloroplast is;as Artari states, a hollow sphere closely lining the membrane, but
with a circular opening at one side. In each chloroplast is a single pyrenoid. When stained with
hematoxylin the single nucleus may be seen.

The new complexes arise by the division of the cell contents into 2, 4, 8, 16, and possibly 32
parts (fig. rx, 1). Each of these becomes invested with a cell membrane, and the enveloping
mother membrane becomes more or less irregularly ruptured and the cell complex is set free. In
this process of division the first visible step is the division of the pyrenoid, then the division of the
chloroplast. At just what time the nucleus divides in reference to the division of the other parts
was not determined. After the chloroplast has undergone one or more divisions the appearance is
that of a cell with several chloroplasts, each with its own pyrenoid. It is a question whether
mistakes have not been made at times by investigators in different species of algze in taking these
portions of the divided chloroplast to be entire chloroplasts and characteristic for the species. The
mother membrane, after it is cast off, remains for a time embedded in the gelatinous substance
(fig. 1x, 2, 8a), but in the older complexes it is no longer visible (fig. Ix, 1, 4).

PLANKTON ALG OF LAKE ERIE. 383

As the type species of Plewrococcus, Plewrococcus vulgaris Menegh., reproduces by means of
simple vegetative division involving both contents and membrane, it would seem that this species
could not rightly be called Plewrococcus. In respect to the mode of reproduction it agrees with
Chlorella, but the presence of the thick, gelatinous envelope is not characteristic for that genus.
The physiological characteristics also of this species vary widely from those of Chlorella. The
correct systematic position seems to be near to AKirchneriella, as the chief point of distinction
between the two forms is the shape of the cells, the cells of this species being spherical, while the
cells of Kirchneriella are crescent-shaped. The formation of cell complexes is the same.

Pieurococcus aquaticus Snow. new species.

Pleurococcus aquaticus shows in its highest development the typical structure of Plewrococcus,
consisting of clusters of cells 2, 4, 8, 16, 32, or even more in number, arranged in cubical form
(fig. x, 1). These clusters arise from the repeated division of cells, alternating in three directions
of space.

The diameter of the cells of a cluster varies from 4 to 7 4. The membrane is thin and gives
no reaction with iodine and sulphuric acid. The chloroplast is single, concave, thin, parietal, a
vivid green in color, and has an opening on one side, which, however, is rarely distinguishable
while the cells are arranged in the cluster. No pyrenoid is present. The small spherical or oblong
nucleus lies near the center of the cell.

The large clusters of cells evidently do not increase indefinitely in size, for after a period,
under ordinary conditions, the cells undergo a dissociation, the contact between them becomes
destroyed, and the cells fall into formless masses (fig. x, 5). The individual cells may then divide
and either produce again the large clusters (fig. x, 1, 4), or they may divide and remain in the
isolated state in which they were (fig. x,2). It has been noticed that if the cells are some distance
apart they produce again the large clusters, but if they are closely crowded, instead of remaining

-united after division, they become separated and exist as many single cells, which, except for the

absence of a pyrenoid, can with difficulty be distinguished from an ordinary Chlorella vulgaris
Beyerinck. They are spherical or, before division, ellipsoidal, and the opening on one side of the
chromatophore is conspicuous. At any time these cells, when separated from each other, again
form large clusters. In large cultures both single cells and clusters were usually present, and in
only one instance were the single cells wholly lacking. This was ina culture started for other
purposes in a tube made from collodion, similar in shape toa test tube. This was. filled with a
0.2 per cent Knop’s solution, the algee inserted and the tube sealed. The whole was then immersed
in a 0.2 per cent Knop’s solution. After a few weeks the increase had been great, but only the
large masses were present. Why the alga did not undergo a dissociation in this mode of
cultivation, as well as in others, was not determined. The cells were also somewhat larger than in
ordinary cultures, all having a diameter of 6.5 to 7 ye (fig. x, 3).

This species was in no case found in fresh material, but was found in a large plankton culture
and also in a culture taken from washings of Chara growing among Scirpus americana Pursh. and
Sagittaria rigida Pursh.,in Squaw Bay, South Bass Island. As it was found in but a single
plankton culture, it is probable that it is one of the many littoral forms which at times are found
in the plankton, and that it had been carried out into the plankton by the action of the water. As
it was never seen except in culture, it is difficult to say in what condition it exists m the natural
state. whether as isolated cells or in large cell complexes. It is probable that the dissociated form
is more usual, as the large cell complexes would be less apt to be overlooked.

Chlorococcum natans Snow, new species.

The cells are spherical or slightly ellipsoidal, the greatest diameter noticed being 13 u.. In
appearance they resemble somewhat Chlorococcum infusionum Menegh., but are smaller in size,
are of a lighter, more transparent green, and the contents, instead of being granular, are mottled,
due to thicker and thinner places in the chloroplast (fig. x1, 1).

The shape of the chloroplast is a hollow sphere through which is a circular opening. On the
side opposite this lies a pyrenoid with a starch envelope. The membrane is of cellulose. In the
young stages there is a single nucleus, but shortly before reproduction the nucleus divides so that,
for a period, the cells are multinucleate.

384 BULLETIN OF THE UNITED STATES FISH COMMISSION.

If the material be cultivated in a 2 per cent Knop’s solution, almost all individuals produce
gonidia; that is, the contents become divided into two, four, or eight portions, as if to produce
zoospores, and these divisions, instead of becoming liberated as zoospores, become invested with a
membrane and germinate while still within the mother membrane. These in turn may produce
gonidia before they become liberated, so that two, and possibly three, generations may be included
within a single cell wall (fig. x1, 2). When cultivated in organic solutions and in 0.4 per cent
Knop’s solution, oblong gonidia are formed, but the enveloping membrane becomes gelatinous, and
the alga passes into a palmella condition (fig. x1, 3).

If the material be transferred from a nutritive solution to water, zoospores are formed. If
transferred from 0.2 per cent or 0.4 per cent Knop’s solution, the shape of the zoospores is cylin-
drical (fig. x1,4). They measure 6.5 to 8 ~ long and 2.5 to 3.25 /¢ broad and they move with a rapid
motion. If the same material be transferred from 0.4 per cent Knop’s solution to organic solution,
the zoospores are oval (fig. x1, 5), 7.8 to 10 long and 5.2 to 6.5 ~ broad, somewhat amoeboid
in nature, and they move with a slow, lethargic motion. Apparently they are the cells which, if
they had not been transferred, would have produced gonidia. The structure in both cases is the
same, there being a concave chloroplast in which is embedded a pyrenoid about equally distant
between the two ends. At the anterior margin of the chloroplast is a red pigment spot. There
are two cilia slightly longer than the cell, and at the base of these, two pulsating vacuoles. The
zoospores become liberated by the mother membrane becoming gelatinous. In the case of the
smaller cylindrical ones, as they expand, the enveloping membrane suddenly gives way at one
point and the spores are liberated either in mass or singly. With the larger oval ones the process
takes place more slowly. They arise by successive division of the contents of a cell (fig. X1, 7).

Although there is a difference in the size of these two kinds of zoospores, there is no indication
that these represented distinct macrozoospores and microzoospores. Apparently the larger size is
more of an abnormal condition of the zoospores, as in all respects the cylindrical form seemed the
more natural. :

The cells in the palmella condition and also the large zoospores resemble greatly Chlamydo-
monas, but the absence of a membrane in the motile form, the short period of motion, and the
mode of growth of the alga in the inorganic solutions all showed a resemblance to Chlorococcum.

Botrydiopsis eriensis Snow, new species.

The younger stages of this species resemble that of Botrydiopsis arhiza, described by Borzi
95, but the later stages differ from that species. The cells are spherical, and when mature have a
diameter of 18 to 21“. In the younger stages the chromatophores are more or less hexagonal
disks, and are closely applied to the membrane, with spaces between them (fig. x11, 2,3). In the
older stages the chloroplasts are relatively smaller, more elongated, and more crowded (fig. xr, 1).

The membrane, which is thin, gives the characteristic reaction for cellulose with iodine and
sulphuric acid. Within the cell no starch, pyrenoid, or oil is present, and the single small nucleus
lies near the center.

The reproduction coincides in the main with that of Botrydiopsis arhiza Borzi, usually 16 or 32
zoospores being formed within a cell (fig. xu, 7). The successive stages of their formation were
not observed, but it is probable that they arise from the repeated bipartition of the contents of the
cell, as in other species of Botrydiopsis. In the mode of liberation of the zoospores this species
deviates from Botrydiopsis arhiza and from other known forms of Botrydiopsis, where the zoo-
spore mass, together with the inner layer of the enveloping membrane, escapes gradually through
a small opening in the outer layer of the membrane. In this species the whole mass remains within
the outer layer until both layers become gelatinous, and after a short period of motion within the
membrane the zoospores one by one break through the membrane and escape.

The zoospores (fig. x11, 5) are 5.2 4 long, 2.5 to 3.25 y« broad, and they possess all of the char-
acteristics of Botrydiopsis zoospores. They are very amoeboid, changing their shape constantly
as they move. Two elongated chromatophores are present, lying on opposite sides of the cells.
One projects farther toward the anterior end than the other, and at the anterior extremity of this
lies the pigment spot. A single flagellum is present. During the amceboid movements, when the
protoplasm happens to project at the anterior end beyond the chloroplast, two contractile vacuoles
may be seen, but they are discernible only under these conditions. The motion of the zoospores

PLANKTON ALG OF LAKE ERIPE. 385

is of short duration, and immediately upon coming to rest they become spherical in shape, but often
retain the flagellum and the pigment spot after the spherical form is assumed. The germin:tion
takes place immediately (fig. x1, 6), the cells increasing in size, and the two chloroplasts becom-
ing divided into 4, 8, and more as the size increases. Very often in old cultures and in vigorous
cultures along the sides of the culture glass at the surface of the liquid the zoospores, instead of
being liberated, germinate within the mother membrane and remain united in a mass long after
the surrounding membrane disappears (fig. xu, 4). Before they are mature, however, they sepa-
rate and have the same appearance as cells which come from the motile spores.

Botrydiopsis oleacea Snow, new species.

This species was first found ina culture from plankton material, but many cells taken to be
the same were also found in fresh collections, the distinguishing characteristic being a large
brownish-red globule near the center of each cell, which as yet has not been found in other
plankton alge. Thecells in the mature stage are either spherical, ovoid, or lemon-shaped, but usu-
ally become more rounded in later stages of existence (fig. x11, 1, 2). The ovoid or lemon-shaped
cells were most often noted when the cells had attained about two-thirds their natural size, the
latter shape being conspicuous on account of the wart-like projection on one or both ends of the
cell (fig. x11, 3,4). The cause of these excrescences was not determined. They occurred on some
but not on all cells of the same culture. The largest cells were broadly ellipsoidal, or almost
spherical, and 13.5 « in diameter.

For some months after this form was placed in culture it was regarded as a Chlorococcwm, so
nearly did the general appearance agree with the characteristics of that genus, the only striking
differences being the shape, the absence of the pyrenoid, and the presence of the large red globule
near the center. On account of the very granular appearance of the cell, due to small globules of
oil, the chlorophyll was thought to be in a single chloroplast, as in Chlorococcum, and the presence
of numerous small chloroplasts characteristic for Botrydiopsis was not suspected until the entire
development was traced. Different phases of reproduction, however, showed such a resemblance
to Botrydiopsis that the chloroplasts were again examined. In some young cells it was evident
that there were several instead of one in each, though these were not distinguishable in mature
cells further than that certain areas seemed slightly darker than others. Many mature cells
appeared almost black, so filled were they with the minute globules of oil. This oil became dis-
solved in absolute alcohol. Iodine with sulphuric acid showed the membrane to be of cellulose,
and hematoxylin brought to view the single small nucleus a little to one side of the center.

The red globule which was always present was at first taken to be a particle of red-colored
oil, but, on account of the color, the ordinary tests could not be used satisfactorily. When
absolute alcohol was added the globule disappeared. Its position is apparently underneath the
layer of chloroplasts. It was noticed that in the formation of the zoospores the globule did not
become divided, but remained in the center throughout the whole process, though it apparently
grew somewhat smaller as the process continued. When the zoospores were liberated it was cast
out with them and had no further connection with the organism. This suggested the appearance
described by Klebs (96), in his work on Protosiphon and Hydrodictyon, where the cell sap did
not enter into the process of zoospore formation and was cast out in the same way when these
were liberated. The same phenomenon has also been noted by the author in an undescribed
species of Botrydiopsis.

The zoospores, of which 2, 4, 8, 16, or more are formed in a cell, arise through the repeated divi-
sion of the entire cell contents, except the red globule, until the final number of zoospores is reached
(fig. xin, 5,6, 7). The zoospores are characteristic for Botrydiopsis, having but a single cilium
and being very amceboid in their motion (fig. x111.8). Though their shape is constantly changing,
the general form is pear-shaped, broadly rounded at their posterior end, and tapering toward the
cilium. In length they vary from 5 to 7.8 4 and in breadth from 3 to5 s at their broadest extrem-
ity. As in the mature cells soin the zoospores the chloroplasts are obscured by oil. In the anterior
end, just at the base of the flagellum, is a very refractive dull red spot, but it could not be deter-
mined whether this was the ordinary pigment spot of the zoospore or the beginning of the red
globule found in the older cells. The zoospores are active and seek the light. On coming to rest
they become rounded and the chloroplasts become more distinct than at any other stage of their

F. C. B. 1902—25

386 BULLETIN OF THE UNITED STATES FISH COMMISSION.

existence. In some cases two chloroplasts are distinguishable in very young cells (fig. x11, 9).
In the liberation of the zoospores the membrane becomes to a certain extent dissolved, then the
zoospores by their motion gradually expand the cell until finally the wall gives way and the spores
escape. The time required for this process varies from 1 to 30 minutes.

When the nourishment of the medium in which the organism grows becomes exhausted. the cells
pass into a resting stage (fig. xu, 10, 11), the contents assume a yellow color, and the membrane
becomes thick. The red globule still remains prominent. In this condition the alga can withstand
being dried, but it quickly changes to the vegetative form when fresh nutritive solution is added.
It was cultivated under many different conditions, but it was constant in all.

Chlorosphera lacustris Snow, new species.

Chlorosphera lacustris resembles somewhat the Chlorosphera angulosa Klebs, but is distin-
guished from it in a number of details, the principal one being the size, the largest cells of this
species measuring 9 to 10.5 4, while those of Chlorosphera angulosa measure from 15 to 30 /.

The shape of the single cell of Chlorosphera lacustris is either spherical, oval, or ellipsoidal
(fig. xIv,1). Asin other species of Chlorosphera, a vegetative division of the cells occurs in three
directions of space, involving both contents and membrane, after which the cells usually remain
connected, forming complexes of two, four, eight, or more cells (fig. xiv, 2, 3). In time these
complexes may fall apart and the cells become spherical, as before division.

The membrane is thin and is composed of cellulose, as the test with iodine and sulphuric acid
shows. The chloroplast lies close to the membrane and is of the same shape as the membrane,
though relatively much thicker. No opening through the chloroplast could with certainty be
detected, though a lighter area at one side was prominent.* Surrounded by the chloroplast is a
pyrenoid with a starch envelope.

The zoospores are 6.5 to 9 long and 2.6 to 4 4 broad; they are slightly broader at the posterior
end than at the anterior (fig. xtv, 4). Two cilia about as long as the cell are present; alsoa pigment
spot. The chloroplast is concave and extends nearly to the anterior end. Two pulsating vacuoles
are found just back of the cilia, and a pyrenoid is embedded in the chloroplast. Four, eight, or
more zoospores are formed from a cell (fig. xIv,7). They are liberated by the membrane becoming
gelatinous at one point, through which first one or two gradually force their way. The others
follow in quick succession, leaving the empty membrane behind. On coming to rest the zoospore
assumes at once a spherical form (fig. XIv, 5) and develops into a mature cell. In this respect it
differs from Chlorosphera angulosa Klebs, as in that species the zoospores retain for some time
the elongated form. They originate by the successive bipartition of the cell contents (fig. xIv, 6).

Though both forms of reproduction, the vegetative division and the production of zoospores,
were found in all cultures, it seemed to reproduce mainly by means of zoospores. Knop’s solution
of 0.2 per cent concentration seemed to be the most favorable medium for development and was
used in tracing the life history. In this solution the zoospores were formed very rapidly, and
when transferred to distilled water they were produced in a much shorter time than is usually
required for the production of zoospores in unicellular algee.

Chlorosphera parvula Snow, new species.

The present species resembles somewhat the preceding species, though, aside from being
smaller, it is easily distinguished from it by the gelatinous nature of the membrane after division,
causing the cells to separate slightly, though held in complexes of 2, 4, or 8 cells (fig. xv, 1, 2).
The two species might also be distinguished by their zoospores, those of the preceding species
being more oval or ellipsoidal than those of this species. The minute points of structure of the
mature cell, however, the chloroplast, the composition of the membrane, and the contents of the cell,
are the same in this species as in Chlorosphera lacustris. The diameter of the full-grown cell
is 7.8 to 9 #. The zoospores (fig. Xv, 3), of which four are usually formed in a cell, are oval or
spherical; when oval they measure 6.5 long and 4.5 to 5 /c broad and the spherical ones 5 to 6 /« in
diameter. They have an obliquely placed concave chloroplast, a pigment spot, two cilia about
1} times the length of the cell, and two contractile vacuoles. The zoospores are formed in the
usual manner, by successive divisions of the cell contents, and are liberated by the gradual soften-
ing of the membrane.

PLANKTON ALG OF LAKE ERIE. 387

Mesocarpus sp.

This small species of Mesocarpus was found so often in the plankton that it might almost be
called a plankton species. At first it could not be recognized as Mesocarpus, for usually the
chlorophyl was greatly reduced and was collected in a very small space at the center of each cell
(fig. XVI, 2), and it was only after the form was placed in culture that it was recognized as belong-
ing to that genus (fig. xv1, 1). As the zygospores were never found, the species could not be
determined with certainty. By means of cultures “in a large number of media it was determined
that the chlorophyl collects under any circumstances that are not favorable, such as in too weak or
or too strong culture media (1 per cent or 0.05 per cent Knop’s solution), or in media that are not
adapted to the plant, as well as in old cultures when the nutrition has become exhausted. It
would appear, then, that when this form occurred in the open lake, the nutrition was not quali-
tatively or quantitatively favorable to its most vigorous condition, though adequate to maintain
its existence and even growth.

Ccelospherium roseum Snow, new species.

Several forms of Celospheerium are almost universally found in the plankton during the
summer months. Some of them are easily recognized, while others are of doubtful name, and the
difficulty of cultivation makes the classification more difficult. One of those most commonly
found is the form shown in fig. xvi, 1. The colonies are 34 to 52 4. in diameter; the cells measure
3.25 to 4 w in diameter, are spherical, pinkish or brownish in color, and are closely arranged or some-
what scattered over the surface of the gelatinous sphere. Indigo solution shows the presence of a
gelatinous covering to the colony, varying in thickness according to conditions. On agar cultures
this covering assumed a diameter almost equal to that of the colony.

Tf the cells are closely arranged, and if the focus of the microscope is on the surface of the
sphere, the colony appears as a typical Celospheerium where the gelatinous sphere is homogeneous
(fig. xvi, 1 a), but if the cells are less closely arranged and the focus is at center the gelatinous
portion may be seen not to be homogeneous, but to consist of a system of dichotomous gelatinous
branches radiating from a common center, bearing the cells on their terminal divisions (fig, xv,
1b), as in Dictyospherium. Between these branches lies gelatinous substance continuous with
that surrounding the colony. The line of demarkation between this substance and the branches is
more or less distinct, according to conditions. In some cases it is hardly distinguishable, while
in others it is sharply defined.

As a solution from a quantity of Anabena flos-aque was the only one in which vigorous
cultures could be obtained, the alga could not be subjected to a very great variety of conditions,
and yet simply transferring from the lake water to this solution produced some change. Always
in cultures the cells became more closely arranged, the branches became indistinct, and in many
cases, apparently when the conditions were less favorable than in the lake, the color changed from
a pink to a brown, though if the concentration of the solution were right the pink color was
maintained. Apparently the distinctness of the branches is controlled somewhat by the density
of the surrounding medium—the denser the medium the denser the surrounding substance, and,
consequently, the less conspicuous the branches. Distilled water seems to be a solvent of this
substance and the cells become detached entirely from the colony. The reproduction of this species
is typical in all respects for Ceelosphcerium as described by Naegeli. If the cells become detached
from the stalks. then division occurs once in three directions of space, and afterwards only in two
directions, both at right angles to the surface of the sphere. As no very small colonies were found
in the plankton, however, it is probable that in nature reproduction usually occurs by the division
of the entire colony into two, rather than that new colonies originate from the separated cells.

Both forms mentioned—the pink, with the visible gelatinous branches, and the brown, where
the gelatinous branches are not visible—were at times found in the plankton, but their identity is
evident. A number of others differing slightly from either of these were found which possibly
may have been connected with these, but as neither could be made to assume the characteristics
of the other artificially, their identity as yet can not be assumed. In one case all traces of the
enveloping gelatinous substance were wanting, and the cells, borne on what seemed to be perfectly
free gelatinous stalks, were moved about freely by the action of the water (fig. xvi, 2). Other

a These cultures were continued for some weeks by Miss Anna L. Rhodes, as well as by the writer.

388 BULLETIN OF THE UNITED STATES FISH COMMISSION.

forms were found with conical or oval cells, which undoubtedly were the Gomphospheeria lacustris
of Chodat, °98, and possibly the Cwlospherium naegelianum as figured by Borge, 00.

The resemblance of the form described, as well as of these other forms, to certain species of
Gomphospheria, such as Gomphospheria lacustris Chodat, is fully recognized by the author, but
a study of the well-known Gomphospheria aponina Kitz, and of the well-recognized species of
Celospherium has caused the writer to place it under the genus Coelospherium rather than Gom-
phospheria. From a study of the true Gomphospheria each cell, instead of simply resting at the
extremity of the stalk, seems to lie in a capsule of the same substance as the stalk and continuous
with it, as has been figured by Schmidle (01). The outer boundary of this capsule is sharply out-
lined about each individual cell, an appearance which has not been noted in any of these other forms.
Further, it would seem that all Cewlospherium species, although the central gelatinous sphere
appears homogeneous, really have at the center the dichotomously branched framework of denser
gelatinous material. If a colony of Celospherium kutzingianum Naeg. be crushed under a cover
glass, it will first divide into two, then into four, and then into eight equal parts, each becoming
spherical immediately, just as would occur if left to take its normal course, whereas if it were
perfectly homogeneous the mass would crush without any system. In all cases of multiplication
where the colony becomes divided into two, evidently the two branches of the first dichotomous
division at the center become detached from each other, and the two halves, unable to hold together
by the less dense gelatinous substance, are set free.

Chroococcus purpureus Snow, new species.

The cells are spherical, or, just before division, somewhat elongated, usually arranged two by
two in colonies of four or eight, all cells of which are more or less separated from each other
according to age, and held in place by an enveloping gelatinous substance. The diameter of the
cells is 13 4; the membrane is thin. The color in the natural condition is grayish purple (fig. Xv).

This species is distinguished from the Chroococcus multicoloratus Wood in being larger, the
cells more loosely associated into colonies, and in possessing a more decided purple color. When
it was first noted in the plankton it was thought it might be a Chroococecus limneticus Lemm..
which is so abundant in the plankton and which differs from it only in color, that being a blue-
green, while this is a purple. Though the two species could not be maintained in artificial culture
for observation during any extended period of time, still, in an organic solution C. purpureius was
kept in a healthy condition for a number of weeks, during which another culture of Chroococcus
limneticus, under identical conditions, was kept for comparison. This was long enough to convince
one that the two forms were not the same and that the purple did not change into the blue-green.
Both this and Chroococcus limneticus, however, did vary their hue somewhat, according to condi-
tions, both taking on a much darker shade of their respective colors as the concentration of the
organic substances in the culture medium was increased. In old solutions both became paler, the
purple form assuming something of a brown tinge and the blue-green a yellowish gray. Under no
conditions, while in a healthy state, did the two alge assume the same appearance. In both species,
however, when cells lost their vitality, the contents contracted, the outline of the enveloping gelat-
inous substance became sharply outlined, and the color became a deep blue-green (fig. XVIII, «).
In this condition they could not perhaps be distinguished. Whole clusters of them were found in
the plankton, and until this phase of these two forms was noted they were supposed to be a species
of Gleocapsa, but were probably only pathological stages of one of these species.

DESCRIPTIONS OF NEW SPECIES.

Chlamydomonas gracilis Snow, new species (fig. 1).

Cells cylindrical, rarely oval or spherical, 10.5 to 13 4 long, 5 to 6.5 2 broad, color a dull bluish
green; cilia 2, about 14 times as long as the cell: pigment spot a dull red disk, often equally distant
from the two ends; pyrenoid at the extreme posterior end. (Gametes (?) oval in shape and some-
what smaller than the vegetative individual. Locality. plankton of Lake Erie.

Chlamydomonas communis Snow, new species (fig. I1).

Shape, ovoid, cylindrical or ellipsoidal, 10.5 to 13 4 long, 6.5 to 8 sc broad; color a light yellowish
green, the pyrenoid near the center; pigment spot an inconspicuous red rod: cilia 2, slightly longer
than the cell; division longitudinal. Locality, plankton of Lake Erie.

a

PLANKTON ALGA OF LAKE ERIE. 389

Chlamydomonas globosa Snow, new species (fig. II).

Cells spherical or slightly ellipsoidal, 5.2 to 7.8 /< in diameter; membrane smooth at anterior
end; two flagella as long or slightly longer than the cell; pigment spot small and inconspicuous;
chloroplast much thickened at the posterior end; pyrenoid present; a pulsating vacuole at anterior

end. Gametes not found. Locality, plankton of Lake Erie.

Fusola viridis Snow, new genus and new species (fig. V1).

Cells fusiform or slightly sigmoid, 27 to 29 “< long and 6.5 to 21 4 broad, each cell surrounded
by a thick, homogeneous, gelatinous envelope, the outer line of demarcation being prominent;
color a bright green. The chloroplast occupies most of the cell except for a small spherical cavity
near the center, in which lies the nucleus; a pyrenoid is present. Reproduction by means of divi-
sion of the contents into two, the halves gradually assuming the shape of the mother cell, during
which process the enveloping membrane becomes obliquely ruptured. Membrane of cellulose.
Large masses of cells may be formed in the presence of a great amount of nutritive substance.
Loeality, a pond on Middle Bass Island, Lake Erie.

Chodatella citriformis Snow, new species (fig. VIII).

Cells ellipsoidal with an obtuse projection at either end; length 13 to 23 4, breadth 8 to 20 wu;
spines slender, forming whorls at the bases of the projections. Chloroplast single, parietal, lying
lengthwise of the cell. Reproduction by division of the contents of the parent cell into 4 or 8,
each part becoming invested with a membrane and thus fcrming a complete individual, Found
in surface and deep tow of Lake Erie.

Pleurococcus aquaticus Snow, new species (fig. X).

_ Cells 4 to 7 « in diameter, existing either as spherical or ellipsoidal individual cells, or as some-
what angled cells combined into large cubical or irregular masses. Membrane thin, chloroplast
concave, with an opening at one side; no pyrenoid. Reproduction by division of membrane and
contents alternating in three directions of space. Locality, the plankton of Lake Erie.

Chlorococcum natans Snow, new species (fig. XI).

Cells spherical or slightly elongated, not exceeding 13 « in diameter. Membrane of cellulose;
chloroplast concave, of the shape of the cell, with a circular opening at one side; nucleus single in
young individuals, but just before reproduction of the same number as the zoospores. In 2 per
cent Knop’s solution the organism often forms gonidia, while in weak organic solution it passes
into a palmella condition in which the cells are oblong. Zoospores 6.5 to 8 u long, 2.5 to 3.25
broad. with two flagella, a concave chloroplast, a pyrenoid, a pigment spot, and two pulsating
vacuoles. Locality, plankton of Lake Erie.

Botrydiopsis eriensis Snow, new species (fig. XII).

Cells spherical, 18 to 21 2 in diameter; the chloroplasts in mature cells elongated and irregu-
larly arranged, in young cells appearing as hexagonal disks closely applied to the membrane.
Zoospores 2.5 /4 long, 2.5 to 3.25 « broad, with two chloroplasts, a single flagellum, a pigment spot,
and two contracting vacuoles. Usually 16 zoospores formed in a cell; when liberated the inner
layer of the mother membrane emerges with the zoospores from the outer layer. MWocality,
plankton of Lake Erie.

Botrydiopsis oleacea Snow, new species (fig. XIII).

Cells spherical, ellipsoidal or lemon-shaped, not exceeding 16 /¢ in diameter, containing numer-
ous minute particles of oil which obscure the outline of the chloroplasts; near the center a large,
prominent, dull-red globule; membrane of cellulose. Zoospores pear-shaped, 2, 4, 8, or 16 in
number, formed from repeated bipartition of the cell contents, excepting the red globule; size of
zoospores 5 to 7, 8 4 by 3 to 5 “; character amceboid; flagellum single at smaller end; pigment spot
present; chloroplasts obscured by oil, two of them discernible in germinating cells. Zoospores
liberated by the softening of the entire enveloping membrane. Under unfavorable conditions a
resting stage is assumed, the membrane becomes thick, and the contents assume a yellow color.
Locality, the plankton of Lake Erie.

390 _ BULLETIN OF THE UNITED STATES FISH COMMISSION.

Chlorosphera lacustris Snow, new species (fig. XIV).

Individual cells 9 to 10.5 /¢ in diameter, spherical or ellipsoidal, usually in complexes of 2, 4,8,
or more, formed by vegetative division, including membrane and contents; chloroplast concave;
pyrenoid present; membrane thin, of cellulose. Zoospores 6.5 to 9 long, and 2.6 to 4 4 broad,
oval, larger at the posterior end; two cilia present, a pyrenoid, a pigment spot, and 2 contractile
vacuoles; 4 to 8 zoospores formed in a cell, liberated by the softening of the membrane at one point.
Locality, the plankton of Lake Erie.

Chlorospheera parvula Snow, new species (fig. XV).

Cells usually in complexes of 4 or 8, more or less separated from each other by the partial dis-
solution of the membrane. Diameter of cells 7.8 to 9 4; chromatophore concave, with a circular
opening near the newest portion of the membrane. Pyrenoid present; membrane of cellulose;
zoospores oval or round, 5 to 6 4c in diameter, 4 formed in each cell, liberated by the softening of
the entire membrane. Locality, the plankton of Lake Erie.

Celospherium roseum Snow, new species (fig. XVII).

Colony 35 to 52 in diameter; cells spherical, pinkish or brown, 3.25 to 4 in diameter, arranged
more or less closely over the surface of the gelatinous center; the gelatinous center not homogene-
ous, but containing a system of dichotomously branched gelatinous stalks, on the ends of which are
borne the cells: in the spaces between the gelatinous branches and surrounding the whole is a less
dense gelatinous substance. Common in the plankton of Lake Erie.

Chroococcus purpureus Snow. new species (fig. XVIII).

Cells spherical, or just before division elongated, usually arranged 2 by 2 in colonies of 4 or 8,
separated from each other and held in place by an enveloping gelatinous substance; color a gray-
ish purple, changing to brown under unfavorable conditions. Cells when dying assume a dark
blue-green, and the gelatinous envelope is sharply outlined. Common in the plankton of Lake Erie.

LIST OF PLANTS DETERMINED IN LAKE ERIE.

In the following list no account is taken of the number of individuals found, or
of the relative number found during the different years, as no accurate quantitative
work was done by the writer; but, had such a study been made, it is probable that
interesting results would have been obtained. For instance, during the summer of
1898 Kirchneriella obesa (West) Schmidle was one of the most common of all the
Chlorophycee found in the plankton, while in 1899 it was found but a very few
times, and in 1900 only occasionally. During its absence in 1899 its place seemed
to be taken by Oocystis borgei, which the preceding year had not been noted at all,
and the next season was found only in very small quantities. An equal variation
was noted in the occurrence of different forms from week to week during each year.
Certain forms, such as Anabena flos-aque, appeared in quantities for a few days
and then disappeared almost altogether. The number of diatoms also varied very
largely at different times. An explanation of such variations would undoubtedly
involve a more accurate knowledge than we now have of the composition of the
water, as well perhaps as of other elements in the environment.

In the collections of the plankton numerous fragments of filamentous algze—
Spirogyra, Zygnema, Mesocarpus, didogonium, and Bolbochete—were often found,
but as no stages of reproduction were present they could not be determined, and so,
except in a few cases, no mention is made of them.

The species that are not starred were taken from the plankton. Those marked
with one star were found in washings of stones and of plants growing in the lake.
Those marked with two stars were found in Lemna Pond, South Bass Island, and
those marked with three stars were found in a stagnant pond on Middle Bass Island.

PLANKTON ALG

OF LAKE ERIE.

List of plants determined in Lake Erie.

CONFERVOIDEE.

Coleochcete scutata Bréb.*
(Edogonium eryptoporum Wittr.*
Prasiola sp.
Stigeoclonium tenue Kg.
Cheetophora endivicefolia LARS
Aphanochete repens A. Br.
Cladophora glomerata Kg.
var. subsimplex Rabh.
Hormidium nitens Menegh.
flaccidum (Kg.) Braun.
Bumilleria sp.

SIPHOPHYCE®

Protosiphon botryoides (Kg.) Klebs.
PROTOCOCCOIDE.

Volvox globator Ehrb.
Eudorina elegans Ehrb.
Pandorina morum Bory.
Synura volvox Ehrb.* i
Gonium tetras A. Br.*
pectorale Miller.*
Chlamydomonas conmunis Snow.
gracilis Snow.
globosa Snow.
Hydrodictyon utriculatum Roth.
Scenedesmus acutiformis Schréde-.
acutus Meyen.
alternans Reinsch.
bijugatus Kitz.
var. flexwosus Lemn.
brasiliensis Bohlin.
caudatus Corda.
var. abundans Kirch.
var. setosus Kirch.
dimorphus Kg.
obliquus (Turpin) Ktz.
opoliensis Richter.
var. carinatus Lemn.

quadricaudatus (Turp.) Bréb.

var. ecornis Ehrb.
Celastrum microporum Nag.
proboscideum Bohlin.
reticulatum (Dang.) Senn.
sphericum Nag.

| Dictyospherium ehrenbergianum Nig.

| Kirchner iella obesa (West) Schmidle.
var. contorta Schmidle.

Golenkinia fenestrata Schréd._

| Citeraleneit parvulum A. Br.*
captitatum Wolle.

Characium ambiguum Herm.
cangustum A. Br.*

| Polyedri tum cruentum Nag.
enorme D. By.*
gigas Wittr.**
lobulatum Nag.
minimum A. Br.*
muticum A. Br.*
ptnacidiuwm Reinsch.
trigonum Nag.*
var. tetragonwm Rabh.

pulchellum Wood.
Hormospora sp.
Tetraspora natans Kitz.
Schizochlamys gelatinosus A. Br.
Fusola viridis n. sp.***
Dimorphococcus lunatus A. Br.***
Porphyridium cruentum Nig.*
Botryococcus braunii Kg.
Gleecystis ampla Rabh.
Nephrocytium agardhianumn Nig.
Oocystis borgei Snow.
lacustris Chodat.
solitaria Witty.
Chodatella citriformis Snow.
Rhaphidium biplex Reinsch.
braunti Nag.
convolutum Rabh.*
faleula A. Br.
minutum Nag.
polymorphum Fres.
Rhaphidium (2) spirale Turner.
Selenastrum acuminatum Lagerh.
bibraianum Reinsch.
gracile Reinsch.
Dactylococcus infusionum Nig.
Stichococcus bacillaris Nig.
Pleurococcus aquaticus Snow.
regularis Artari.
Chlorella infusionum Beyerinck.
vulgaris Beyerinck.

NotTEe.—A specimen was found agreeing 1n every re-
spect with Celastrum cubicum Nig., which produced
typical ccenobia of Celastrum probose ideum, so that the
svecies of Celastrum cubicum is to be questioned.

Chlorococcum infusionum Rabh.
natans Snow.

Sorastrum spinulosum Kg.*
Pediastrum boryanum Menegh.
var. longicorne Reinsch.
constrictum Hass.**
ehrenbergii A. Br.*
pertusum Kitz.
var. brachylobum A. Br.
var. clathratum A. Br.
var. microporum A. Br.
rotula Ehrb.*
sturmii Reinsch.
Staurogenia apiculata Lemn.

quadrata (Morren) Kitz.

rectangularis Nag.
Kirchneriella lunaris (Kirch.) Mob.
var, diane Bohlin.

| Botrydiopsis eriensis Snow.

Chlorosphera lacustris Snow.
parvula Snow.

Scotinosphera paradoxa Klebs.

CONJUGATE,

| Mesocarpus sp.

Hyalotheca dissiliens Bréb.

Onychonema leeve Nordst.
var. minus.

| Spheerozosma filiforme Rabh.

Closterium acerosum Ehrb.
diance Ehrb.
ehrenbergti Meneg.
leibleinii Kg.
lineatum Ehr.**

B91

BULLETIN OF TIT

UNITED

STATES FISH COMMISSION.

List of plants determined in Lake Hrie—Continued.

CONJUGAT A.

Closterium pronum Bréb.
var. acutum Klebs.
var linea Klebs.
Pleurotenium trabecula Nig.
Cosmarium crenatum Ralfs.
euastroides N.
granatum Bréb.
kjellmanii Wille.
meneghinii Bréb.
var. concinum Rabh.
punctulatum Breb.
pygmoeeum Archer.
ralfsii Bréb.
var. typicum Ralfs.
reniforme Ralfs.
tetraopthalmum Kiitz.
tinctum Ralfs.
Euastrum binale Ralfs.
verrucosum Ehrb.
Staurastrum crenulatum Nig.**
gracile Ralfs.
oblongum N.
polymorphum Bréb.
var. cheetoceras Schroéd.
striolatum (Niig.).
teliferwm Ralfs.

BACELLARIACE At,

Navicula cryptocephala Kg.*
limosa Ag.
longa Ralfs

Pinnularia major Sm.**

radiosa Sm.*

Stauroptera parva (Ehrb.) Kirch.**

Stauroneis fenestra Sm.**

phenicenteron Ehrb.*

Amplhiprora ornata Bail.

Pleurosigma attenuatum Sm.*

Amphora ovalis Kg.*

Cymbella maculata Kg.
rotundata H. H. C.

Encyonema prostratum Ralfs.

Cocconets placentula Ehrb.*

Cocconema cistula Hempr.

lanceolatum Ehrb.

Gomphonema acuminatum Ehrb.

capitatum Ehrb.
constrictum Elrb.
intricatum Kg.*

Achnanthes exilis Kg.*

Nitzschia linearis Sm.**
sigmoidea Sm.

Campylodiscus cribrosus Sm.

Cymatopleura solea Bréb.

elliptica Bréb. *

Surirella ovalis Menegh.
saxvonica Auersw.
splendida Kg.

Synedra oxyrhynchos Kg.

ulna Ehrb.
var. longissima Wm. Sm.

BACELLARIACK As.

Fragilaria crotonensis (A. M. Edwards) Kitton.

virescens Ralfs.
Asterionella formosa Hassal.
Tabellaria fenestrata (Lyng) Kg.
flocculosa Kg.
Epithemeia ocellata Kg.**
turgida Kg.**
ventricosa Kg.**
zebra Kg.

| Melosira arenaria Moore.

granulata (Ehrb.) Ralfs.
varians Ag.
Orthosira orichalcea Sm.
Cyclotella comta (Ehrb.) Kutz.
dubia Hilse.
meneghiniana Rabh.*
striata (Kutz.) Grun.
Stephanodiscus niagara Ehr.

SCHIZOPHYCE 4,

Rivularia radians Thur.
var. dura Kirch.
var. minutula Kirch.
Mastigonema cerugineum Kirch.
Alphanizomenon flos-aquee Allman.
Anabeena flos-aque Kg.
var. circinalis (Rabh.) Kirch.
Plectonema mirabile Thur.
Oscillatoria erugineo-cerulea Kg.
chalabea Martens.
freehlichii Kg.*
imperator Wood.*
natans Ke.
subtilissima Kg.
tenerrima Kg.
tenuis Ag.
Lyngbya wollei Farlow.
Microcoleus anguiformis Harv.
Merismopedia elegans A. Br.
glauca Nig.
kittzingti Nig.
tenuissimum Lemm.
violacea Kg.**
Ceelospherium kittzingianum Nig.*
roseum Snow.
Clathrocystis ceruginosa Henfr.
roseo-persicina Cohn.
Gomphospheria aponina Kg.
var. aurantiaca Bleisch.
Polycystis icthioblabe Ke.
Gloeocapsa fenestralis Kg.
punctata Nag.
Chroococcus pallidus Nig.
limneticus Lemm.
purpureus Snow.

PHYCOMYCETES.
Beggiatoa leptomitiformis Trevis.

arachnoidea Rabenh.
Spirochete plicatilis Ehrb,

PLANKTON ALGA OF LAKE ERIE. 393

LITERATURE.

ARTARI, A.
1892. Untersuchungen tiber Entwickelung und Systematik einiger Protococcoideen. Inaugu-
ral-diss. Basel. Moskau.
1901. Zur Ernihrungsphysiologie der griinen Algen. Berichte der Deutschen botanischen
Gesellschaft, Bd. x1x, No. 1.
Boxorny, TH.
1894. Ueber die Betheiligung chlorophyllfithrender Pflanzen an der Selbstreinigung der Fliisse.
Archiv fiir Hygiene, xx.

BorGg, O.

1900. Schwedisches Stisswasserplankton. Bot. Not.
Borzi, A.

1895. Studi algologici. wu. Palermo, 1895.
CuopatT, R

1896. Matériaux pour servir a l’histoire des Protococcoidees. Bull. de l’Herbier Boss., v.
1897. Etudes de biologie lacustre. Bull. de 1’Herbier Boss., v, No. 5.
1898. Etudes de biologie lacustre. Bull. de l’Herbier Boss., v1, No. 1.
Kiess, G.
1886. Ueber die Organisation der Gallerte bei einigen Algen und Flagellaten. Untersuchungen
aus d. botan. Institut, Tiitbingen, 1.
1896. Die Bedingungen der Fortpflanzung bei einigen Algen und Pilzen. Jena. 1896.
KNOrRICH, F. W.
1901. Studien tiber die Ernihrungsbedingungen einiger fiir die Fischproduction wichtiger
Mikroorganismen des Sitisswassers. Forschungsberichte aus d. biolog. Station zn
Plén, Theil 8.
LEMMERMANN, E.
1898. Beitrige zur Kenntniss der Planktonalgen. 1. Botan. Centralblatt.
1898. Forschungsberichte aus d. biolog. Station zu Plén, Theil 6.
PIETERS, A. J.
1901. The plants of western Lake Erie. Bull. U. 8. Fish Comm. 1901, 57-79, 10 plates.
SCHMIDLE, W.
1901. Ueber drei Algengenera. Berichte der Deutschen botan. Gesellschaft, x1x, No. 1.
SENN, G.
1899. Ueber einige coloniebildende einzellige Algen. Botanische Zeitung.
STROHMEYER, O.
1897. Die Algenflora des Hamburger Wasserwerkes; ein Beitrag zur Frage der Selbstreinigung
der Fliisse. Leipzig.

394 BULLETIN OF THE UNITED

EXPLANATION

PLATE I. |

I. Chlamydomonas gracilis Snow.
1,2. Motile cells.
3. Gamete (7).
4. Copulation of gametes’.
I. Chlamydomonas communis Snow.
1-3. Motile cells.
. Chlamydomonas globosa Snow.
1-5. Motile cells.

. Scenedesmus bijugatus var. flecuosus Lemm.
1. Cenobium of 82 cells.
2. Resting stage.

. Staurogenia apiculata Lemn.

1. Compound ccenobium of 64 cells.

2. Compound ccenobium of 16 cells, showing
gelatinous envelopeas brought out by tan-
nate vesuvine.

3. Mass of cells from .05 per cent Knop’s solu-
tion.

4. Single ccenobium in early stages of repro-
duction, taken from an organic solution.
(a) Nucleus. (b) Pyrenoid.

5. Single coenobium.

6. Diagram showing relative position of nuclei
and pyrenoids in young coenobia. («@) Nuc-
leus. (b) Pyrenoid.

7. Membrane of a ccenobium after daughter
eccenobia have been liberated. |
8. Cell showing nucleus and pyrenoid,

(a) Nucleus. (b) Pyrenoid.

’ PLATE II.

VI. Fusola viridis Snow.
1-4. Different stages in process of division.
(a) Ruptured membrane of mother cell.
83. Typical cells.
VII. Oocystis borgei Snow.
1. Single cell showing nucleus, a.
2. Young cells from a culture in organic
solution.
3. Cells after division of chromatophore.
Taken from organic solution.
4. Small colony taken from organic solu- |
tion. :

5. Single cell from 0.05 per cent Knop’s so-
lution, showing remnant of mother |
membrane, b.

VIII. Chodatella citriformis Snow.

1. Mature cell seen from side.
2. Cell seen from end.
3. Cell showing reproduction.

IX. 1-4. Plewrococcus regularis Artari.

1. Complex from the plankton.
2-4. Clusters from a culture.
5. Celastrum microporum Niig.

STATES FISH COMMISSION.

OF FIGURES.

PLATE III.

X. Plewrococcus aquaticus Snow.

1. Cell complex.

2. Individual cells before formation of clus-
ters.

3. Complexes grown in collodion tubes.

4. First stages in formation of complexes.

5. Disintegration of the larger complexes.

XI. Chlorococeum natans Snow.

1. Mature cell.

2. Gonidia formed in 0.2 per cent Knop’ssolu-
tion.

3. Gonidia formed in0.4 per cent Knop’s solu-

tion.
. Typical zoospores.

5. Zoospores formed when material is trans-
ferred from Knop’s solution to organic
solution.

6. Germinating zoospores.

7. First stage in formation of zoospores.

XII. Botrydiopsis eriensis Snow.

1. Mature cell.

2,3. Young cells.
4. Gonidia formed from nonliberation of
zoospores.
3. Zoospores. (Free hand.)
6. Germinating zoospores.
7. Zoospores before liberation.
XII. Botrydiopsis oleacea Snow.
1,2. Mature cells.
3,4. Younger cells of different shapes.
5-7. Different stages in the formation of the
zoospores.
8. Zoospores.
9. Germinating zoospores,
10-11. Resting condition.

PLATE IV.

Chlorospheera lacustris Snow.
1. Single cells.
2,3. Complexesarising from division.
4. Zoospores.
5. Germinating zoospores.
6,7. Stages in the formation of the zoospores.
. Chlorosphera parvula Snow.
1,2. Complexes formed by division.
3. Zoospores.

—

XIV.

XVI. Mesocarpus spec.
1. Normal filament.
2. Filament under unfavorable conditions.
XVII. Ce@lospherium roseum Snow.

1. Typical individual. a. Surface view.
b. Interior view.
2. Celospherium (?) showing free dichoto-
mous gelatinous branches.
Chroococcus purpureus Snow.
Showing mode of growth in small clusters

embedded in gelatinous substance.

XVIII.

BULL. U. S. F. C. 1902 PLATE |

2
1
1 2 a i
a XS 3
25
\
f Hl
ff
ee Sa
3
\. a
: 4
rr
Rae 4 i. Chlamydomonas globosa
1. Chlamydomonas gracilis il. Chlamydomonas communis ;

1V. Scenedesmus bijugatus
yar. flexuosus

J. W. S. del : \ HORN & CO LITHOCAUSTS BALTIMORE

PLATE Il

1902

BULL. U. S. F. C.

vi. Fusola viridis

VIl. Oocystis borgei

Vill. Chodatella citriformis

ococcus regularis Artari

IX. Pleur

ric. BAU

AKOERO 50,1

oD
vo
7)
S
s

BULL. U. S. F. C. 1902 PLATE Ill

X. Pleurococcus aquaticus

2
AS
65 & Ki EN
13 fig)
<r
ee x [
~
8
: YS ;
5 ll id £ |
=A A Caen ®

Eeed es e « @.
es * * e

—

Xil. Botrydiopsis eriensis
Xlll. Botrydiopsis oleacea

ANOER 8 CO,LITHOSAUST:S BALT

PLATE IV

. 1902

BULLS USS: E.G

Bas 8 re, ae Wh
Se « 3. a) a

: oo, gre. a Se »

: 4 2) oe

ee ; ‘ao 4 ae 2

oO
Y | oe XVII

Coelosphaerium ?

/
/ /
/ /
Dole ae a, = /
ei oe 4 »
> aes a! ls J
; vl \ Vi
x \ va
¢ mS wa XVIII
Nee ee
ae
ee | Whroococcus mupuze
Y Fart

xv. Chlorosphaera parvula

-

3 9088 0098