ISOLATION, PURIFICATION, NUTRITION 



35 



in this experiment to facilitate maintenance of the solutions at the 

 desired pH levels. The pH of the cultures in which there was little 

 or no growth was adjusted every twenty-four hours. In the cul- 

 tures in which considerable growth developed, however, adjust- 

 ments were made every twelve hours so that the pH was main- 

 tained within half a unit of the specified values. In these cases it 



Table 3 — Effect of pH of the culture medium and the presence of Na2C03 

 and Na2Si03 on the growth of Coccochloris Peniocystis. Cultures 

 A to H inoculated on Feb. 20, 1950 and harvested on March i, 1950. 

 Cultures H, I, and J inoculated on Nov. 9, 1949 and harvested on 

 Nov. 18, 1949. 



Culture 



Treatment 



Oven-dry wt. of algae 

 (mg. per 400 ml. solution) 



A Basic solution with 3 X NO3 but no Na2C03 no growth 



pH adjusted daily to 5.0. 



B As A, pH adjusted daily to 6.0. no growth 



C As A, pH adjusted daily to 7.0. 4.9 



D As A, pH adjusted daily to 8.0. 12.7 



E As A, pH adjusted daily to 9.0. 40.8 



F As A, pH adjusted daily to 10.0. 69.2 



G As A, pH adjusted daily to 11.0. 48.4 



H Basic solution with 3 X NO3, and pH not 27.2 



adjusted. Inidal pH, 8.4; final pH, 10.3. 



I As H, except both Na2C03 and NaoSiOs 22.1 



omitted. pH adjusted daily to that of 



treatment H on same day. 



J As I, but pH not adjusted. Initial pH 6.7; 3.9 



final pH 7.5. 



was impractical to maintain sterile conditions, but this is the only 

 experiment to be reported in which the cultures were not kept free 

 of contaminants. 



The results presented in Table 3 show that Coccochloris Peni- 

 ocystis requires an unusually high pH for maximum growth. 

 There was no growth in cultures maintained at pH 5.0 and 6.0, 

 and only very slight growth at 7.0 and 8.0. Growth increased con- 



