16 H. C. BOLD 



not occur, one is confronted with another apparent exception to 

 the phenomenon of diffusion as it relates to Hving cells. Such 

 basic problems as these are readily approachable by the tech- 

 nique of pure algal cultures. 



The persistent and insistent report of nitrogen fixation by 

 certain Cyanophyta indicates the need for further study of this 

 group and their activities particularly in soils, while the occa- 

 sional faintly whispered claims of a similar nature for certain 

 soil-inhabiting Chlorophyta merit studies of their role in the soil 

 flora. Furthermore, the Cyanophyta afford an excellent field for 

 the application of pure culture techniques in both morphological 

 and physiological studies. Only a start has been made, for exam- 

 ple in such recent studies as those of Fogg (1944, 1948), in ob- 

 taining data to explain the significance of heterocyst and akinete 

 formation. Very little is known of the germination and subse- 

 quent development of these reproductive cells — data which again 

 could be obtained through the application of pure culture tech- 

 niques. Finally, the important studies of van Niel (1935) on the 

 photosynthesis of pigmented bacteria suggest that basic data may 

 be forthcoming from a study of photosynthesis of Cyanophyta 

 grown in pure culture. 



In the field of algal physiology little is known about the nutri- 

 tion, growth requirements and metabolism of such groups as the 

 Chrysophyta, Pyrrhophyta, and Euglenophyta. With the excep- 

 tion of a few genera of the last two groups scarcely any have 

 ever been studied in uni-algal or pure cultures. 



Although we hear and read a great deal about studies of sex- 

 uality and its genetics and physiology in Chlamydomonas, how 

 much more might be learned from similar studies of diatoms, 

 desmids and filamentous genera! Cytological observations would 

 undoubtedly increase our knowledge of all these groups, were 

 a continuous and abundant supply of material available in con- 

 trolled laboratory culture. 



Finally, with the modern emphasis on possible augmentation 

 of our agricultural commodities directly or indirectly by mass 

 cultivation of algae, studies of the techniques of such cultivation 

 based on exact knowledge of their nutritional requirements like 



