* 
6 MIDLAND NATURALIST. 
Oedogonia, a very small form of monoecious Bulbochaete, all 
more or less abundantly in fruit. Not more than a hundred yards 
from this spot in a pool was found Mougeotia mirabilis Al. Br. 
in all stages of sexual reproduction by lateral conjugation and 
in such large quantities that it could be raked out of the water 
in masses of two or three pounds at a time. Some miles away 
another pool was found containing Cosmarium botrytis rather 
abundantly in conjugation, and Penium margaritaceum not so 
commonly fruiting and a small amount of several species of vegeta- 
tive Closterium. 
he water containing the Cosmarium bioculatum was 
collected in vessels and the plankton concentrated by decantation 
of water, and taken to the laboratory where the material was 
studied. Some was fixed and the rest kept alive in aquaria. 
Several quarts were taken daily between the first and the 13th of 
May, after which date the specimens began to disappear gradually. 
Material transferred to the laboratory was invariably arrested in 
its growth after removal from its native habitat. The Cosmarium 
bioculatum continued to produce asexual spores but subsequent 
development of the full developed spores ceased. The full grown 
spores of the Cosmarium bioculatum and the zygospores of the 
other forms remained in the laboratory for a long time but neither 
could be brought to germination. After persisting in the aquaria 
for months alive they eventually disappeared, leaving no trace. 
The following year the stream and all the adjacent pools were 
carefully examined every few days for a reappearance of the 
‘plants. Only a few vegetative Staurastrum specimens were found 
and no Cosmarium bioculatum whatever. From the live material 
examined at the time of collection the following observations were 
recorded. The fixed and preserved material now in the laboratory 
jars is quite as good fer the description of the processes as it contains 
all the various stages in the formation of the spores. 
Staurastrum rugulosum, Breb. and Staurastrum polymorphum, 
Breb. were found, mostly in the latter stages of zygosporic repro- 
duction the former so abundantly that the zygospores are more 
common in the material than the vegetative forms. Few early 
stages were found most of the zygospores having already fully 
developed spines with hooks. . 
oth vegetative and asexually reproducing stages of  Cos- 
marium  bioculatum, were extraordinarily abundant, though 
vegetative division of the cells was uncommon, and all the stages 
of the formation of the resting spore could be studied. These 
