ISOLATION, PURIFICATION, NUTRITION 37 



heavy precipitates formed in these solutions and made accurate 

 dry-weight determinations impossible, it was evident from visual 

 observation that both treatments produced more growth than 

 the basic solution. Systematic lowering of the concentration of 

 one element at a time from triple to double the concentration, and 

 to the level of the basic solution showed that higher nitrate con- 



Table 4 — Effect of varying the concentration of nitrate in the nutrient 

 solution on the growth of Coccochloris Peniocystis. Cultures inocu- 

 lated on Nov. 10, 1949 and harvested on Nov. 17, 1949 and Nov. 22, 

 1949. 



Oven-dry weight of algae 

 (mg.per 400 ml. solution) after ^^ ^^ ^^^^^-^^ 



Culture NO3 concentration 7 days 12 days after 12 days 



centrations were solely responsible for the increases in growths. 

 The difference in yields between double and triple strength nitrate 

 was very slight, but, in order that yields would not be limited by 

 a deficiency of nitrate, in all subsequent mineral nutrition experi- 

 ments the nitrate concentration in the culture solution was 3 times 

 that of the basic solution. 



Varying the Concentration of the Essential Elements 



Table 4 shows the dry weights of Coccochloris Peniocysiis 

 obtained after seven and twelve days of growth in solutions vary- 

 ing in nitrate concentration from 3 times to i/40th the concentra- 

 tion in the basic solution. Two of the four cultures of each treat- 



