Cytology and Movements of the Cyanophycece. 275 



Gloeocapsa polydermatica, Oscillaria imperator, Oscillaria 

 Froehlichii, Oscillaria nigra, Cylindrospertnum macrospcr- 

 mum, Spermosira litorea, Anabaena Hos aquae, Tolypothrix 

 lanata, Rivularia pisum, Gloeotrichia and Spirulina. 



Methods Employed. 



One of the chief things to be determined in the study of 

 the Cyanophyceas is the best method of preparation of the 

 material. In fact this is as important as the selection of the 

 material itself. The Cyanophyces 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 algse. 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. Not a little of the con- 

 fusion in the interpretation of the cell contents of the Cyano- 

 phycese 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- 



