Cytology and Movements of the Cyanophycee. 275 
Gloeocapsa polydermatica, Osctllaria imperator, Oscillaria 
Froehlichu, Oscillaria nigra, Cylindrospermum macrosper- 
mum, Spermosira litorea, Anabaena flos aquae, Tolypothrix 
lanata, Rivularia pisum, Gloeotrichia and Spirulina. 
Methods Employed. 
One of the chief things to be determined in the study of 
the Cyanophycez is the best method of preparation of the 
material. In fact this is as important as the selection of the 
material itself. The Cyanophycee are amongst the most 
delicate of organisms that one can find in their reaction to 
environmental conditions, regardless of the varying sur- 
roundings under which different species will grow. For 
example, if organisms which ordinarily grow upon a moist 
substratum be subjected to increased moisture, the granular 
contents of the cells are modified or changed altogether. It 
is, therefore, absolutely necessary that in the cultures kept in 
the laboratories for study, the conditions of nature be simu- 
lated more closely than with any other of the alge. This 
is no easy task, and many times in the midst of an interest- 
ing investigation, the culture would die and leave much of 
the accomplished work of little value. Nota little of the con- 
fusion in the interpretation of the cell contents of the Cyano- 
phycez is due to a misappreciation of this point, as is evi- 
denced by the methods of culture described in the various 
papers upon these organisms. Another point to be noted 
is the time of year when experiments are performed. A 
large part of the material used in the present investigation 
was found in various places in the greenhouses of the Uni- 
versity, but even here, where the conditions seemed to be 
ideal, and where the requisites for normal growth were 
fairly constant through the whole year, the organisms 
showed a remarkable tendency to grow in cycles. Beginning 
at a certain period of the spring, they vegetated very rapidly 
and at such times dividing cells would be abundant. Grad- 
