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J. J. SKINNER 



of nitrates. Cultures Nos. 1 to 4 are composed principally of 

 phosphate; Nos. 5 to 8 principally of nitrates, and Nos. 9 to 12 

 principally of potassium. The total green weight of the high 

 phosphate cultures (Nos. 1 to 4) was 15.18 grams in the solutions 

 without vanillin, and 11.12 grams with vanillin. In the high 

 nitrate cultures (Nos. 5 to 8) the weight without vanillin was 

 15.29 grams against 15.35 grams for the cultures with vanillin. 

 In the high potash cultures (Nos. 9 to 12) the weight without 

 vanillin was 17.94 grams, against 11.55 grams for the cultures 

 with vanillin. It is apparent that in the solutions composed 

 principally of nitrate the vanillin had practically no effect, and 

 in culture No. 5, composed of all nitrate, the growth in the 

 vanillin culture was larger than in its control. 



The growth of the cowpeas without and with vanillin in solu- 

 tion Nos. 3, 7, and 11 is shown in figure 1. Here it is shown that 



."'*<. 



Fig. 1. Effect of vanillin on cowpeas in nutrient solutions of different com- 

 positions. (No. 3, nutrient solution containing 48 p. p.m. P2O5, 16 p. p.m. NH3, 

 16 p. p.m. K2O. No. 3a, Same + 100 p. p.m. vanillin. No. 7, nutrient solution 

 containing 16 p. p.m. P2O5, 48 p. p.m. NH3, and 16 p. p.m. K2O. No. 7a, Same + 

 100 p. p.m. vanillin. No. 11, nutrient solution containing 16 p.pm. P2O5, 16 

 p. p.m. NH3 and 48 p. p.m. K2O. No. Ua, Same + 100 p. p.m. vanillin). 



the growth in solution No. 7, composed of 16 parts per million 

 P2O5, 48 parts per million NH3 as nitrate, and 16 parts per mil- 

 lion NoO, is as good in the solution with vanillin as in its check, 

 which contains no vanillin. 



