246 . BOTANICAL GAZETTE [September 



phosphate under different conditions, acid, neutral, and alkaline. 

 These requirements are met by using sodium salts instead of 

 calcium, and employing all three sodium salts of phosphoric acid, 

 namely, the monosodium phosphate (NaH 2 P0 4 ), which like the 

 calcium acid phosphate of the first experiment is decidedly acid 

 in reaction; the disodium phosphate (Na 2 HP0 4 ), which is neutral 

 toward phenolphthalein; and the tribasic sodium phosphate 

 (Na 3 P0 4 ), which is alkaline in reaction. In all other respects the 

 culture solutions were the same in concentration and composition 

 as described in the earlier paper, the full number of 66 cultures as 

 there described being used, both with and without the cumarin 

 and, as in the paper cited, comparisons are always made between 

 solutions of like composition as far as the mineral salts are con- 

 cerned. This comparison, of course, can be made between indi- 

 vidual cultures of like composition or between groups of cultures, 

 when members of like composition occur in both groups. 



Effect of monosodium phosphate 



The 66 culture solutions of equal concentration (80 p.p.m. of 

 P 2 O s +K 2 0+NH 3 ), but varying in composition as far as the ratios 

 of phosphate, potash, and nitrate are concerned, were prepared 

 according to the scheme presented in the earlier paper cited. 

 The sets were always in duplicate, the one containing only the 

 nutrient salts and considered as the normal set, the other contain- 

 ing in addition to the salts 10 p.p.m. of cumarin. The plants 

 grew from October 17 to 29. The green weight at the termination 

 of the experiment for the growth in the 21 cultures composed of 

 mainly phosphatic fertilizer (one-half and more of the nutrients 



grams 



milarly the green weight of 



composed of ma 



grams, and in the cultures composed mainly of potassic fertilizers 

 it was 41.8 grams. The results in the normal set were: for the 

 mainly phosphatic fertilizers, 39.3 grams; for the mainly nitroge- 

 nous fertilizers, 49.9 grams; for the mainly 



46.9 grams, 

 gives the resu 

 taken as 100. 



These results are tabulated in table I, which also 



terms of the normal culture 



