278 University of California Publications. [Botany 



ules. The color was more of a "grass green" than a "blue 

 green," which seems to indicate that the phycocyanin is first 

 used up or disappears first under these conditions. This same 

 material was then placed in the light and kept moist. It assumed 

 its original color again, and grew for three months afterward. 



To induce a resting condition in the cell, I have succeeded 

 best by placing healthy material on compact wet earth and cover- 

 ing the vessel in which it was placed with glass in such a way as 

 to allow evaporation to take place slowly until the material was 

 completely dry and brittle. On wetting this material again and 

 applying stains, it was found that at least 90 per cent, of the cells 

 were in a resting condition, and that the nuclei were a little more 

 concentrated in the center of the cell than they were in the 

 actively growing plants, although otherwise the cell organs ap- 

 peared to be the same as before. 



VI. THE RELATION OF CYANOPHYCEAE TO 

 BACTERIA. 



The relation of the Cyanophyceae to the Bacteria, particu- 

 larly to the sulphur bacteria, has been a subject of research by 

 a number of investigators. Among those who have given special 

 attention to the cytology of these organisms are Biitschli, Fischer, 

 and Macallum. 



In Beggiatoa, Biitschli was able to demonstrate a deeply stain- 

 ing part in the center of the cell and a lighter staining peripheral 

 portion. In B. alba this peripheral portion he found to be very 

 narrow. He looks upon the central portion as the analogue of a 

 nucleus. Fischer and Macallum did not succeed in bringing out 

 this differentiation. Macallum demonstrated the presence of 

 "masked" iron and organic phosphorus uniformly distributed 

 throughout the protoplast of B. alba and B. mirabilis. 



The writer has given but little attention to these organisms, 

 having worked upon but a few forms of the sulphur bacteria, 

 chiefly of the genus Beggiatoa. These forms are usually so filled 

 with sulphur granules that it is difficult to study the structure of 

 the protoplast while these are present. They may readily be re- 



