36 GERLOFF, FITZGERALD, AND SKOOG 



siderably at pH 9.0, reached a maximum at pH lo.o, then decHned 

 again at pH ii.o. 



If other blue-green algae require as high a pH for maximum 

 growth as Coccochloris Peniocystis, nutrient solutions suitable for 

 their culture must contain not only the proper concentrations of 

 die essential elements, but salts must be selected that will maintain 

 the pH of the medium above 8.0. Possibly, therefore, the alkaline 

 buffering provided by the NaoCOg and Na2Si03 may account for 

 the general suitability of Chu No. 10 solution for the culture of 

 blue-green algae. This is indicated by Treatments H, I, and J of 

 Table 3. Treatment H is the basic solution with 3 times NaNOo. 

 In Treatment I, NaoCOo and NasSiOs were omitted from the nu- 

 trient solution, but the pH of the solutions was adjusted daily to 

 those of Treatment H in which the pH gradually increased from 

 8.3 when inoculated to 10.4 at the time of harvest. There was only 

 a slight difference in the yields from these two treatments. In 

 Treatment J, however, in which NagCOa and NasSiOg were 

 omitted from the basic solution and the pH was left unadjusted, 

 there was almost no growth. Similar results have been obtained 

 with Nostoc muscorum Kiitz. which show that NaaCOs and 

 Na2Si03 need not be added to the culture medium to provide es- 

 sential elements, but that their favorable effect for culturing at 

 least diese two species is related to their alkaline buffering ca- 

 pacity. 



Concentrations of Essential Elements Necessary for 



Maximum Growth 



Before starting experiments to determine the effects of vari- 

 ations in the concentration of a single element on the growth of 

 Coccochloris Peniocystis, it was necessary to ascertain if the basic 

 solution, as presented in Table 2, contained at least optimal 

 amounts of all the essential elements for the maximum growth 

 of this organism, so that only the elements under investigation 

 could become limiting. Consequently, culture solutions were 

 prepared in which all the constituents were present at 2 times 

 or 3 times the concentrations in the basic solution. Although 



