ISOLATION, PURIFICATION, NUTRITION 31 



Twenty-two species of blue-green algae have been isolated 

 by the above procedure. All but one of these have been identified 

 by Dr. Francis Drouet of the Chicago Natural History Museum 

 and are listed in Table i. For some cultures (1020, 1021, 1029, 

 1036, and 1042), the more familiar equivalents are included with 

 the names assigned to them by Dr. Drouet. The new names given 

 these species have been published by Drouet and Daily (1948) 

 and are to be fully explained and discussed in a revision of the 

 Chroococcaceae they are now preparing for publication. The 

 number assigned to each culture is the number by which that 

 particular species is identified in this laboratory, and that by 

 which it will be designated as a permanent specimen in the Chi- 

 cago Natural History Museum collection. 



Two species (1013 and 1042) which have been obtained from 

 Dr. Robert Emerson of the University of Illinois are also included 

 in Table i. In addition, this table gives, where available, the date 

 on which each species was isolated and the approximate time 

 required for maximum growth to develop after inoculation into 

 flasks of Chu No. 10 solution. 



The time required for maximum growth varies widely witK 

 the species. For example, Coccochloris Peniocystis (Kiitz.) 

 Drouet and Daily, Diplocystis incerta (Lemm.) Drouet and 

 Daily, and Diplocystis aeruginosa (Kiitz.) Trevis (cultures 1020,. 

 1021, and 1036) reach a maximum in only 10 to 12 days, whereas 

 Calothrix parietina (Nag.) Thur. and Lyngbya Birgei G. M. 

 Smith (cultures 1018 and 1026) require 40 to 50 days. However, 

 as mentioned previously, these relative rates of growth can be 

 considered specific only with Chu No. 10 solution as the culture 

 medium. 



Bacteria-Free Cultures 



Bacteria normally penetrate and live in the gelatinous sheaths 

 which surround the cells and filaments of blue-green algae so that 

 their removal by plating, washing, or dilution is very tedious 

 and difficult, if not impossible. For this reason, ultra-violet irra- 

 diation, employed by Allison, et al. (1930, 1937) to obtain a bac- 



