38 



BOTANICAL GAZETTE 



[JULY 



cumann 



In table II are given the results for the P 2 5 , 



NH,, and KX), separately, under the normal 



cumarin set. 



TABLE II 



Total milligrams of p 2 o 5 , nh 3 , and k 2 o removed from the 36 culture 



containing all three of these ingredients 



Total absorption in milligrams 



Normal 



PA 



NH 3 

 K 2 



Cumarin 



Relative 



278.5 

 482.6 

 618.2 



Percentage of 



cumarin cultures 



above normal 



264. 5 



415-3 

 592.6 



95 

 86 



96 



57 

 22 



39 



An examination of these figures discloses the fact at once that 

 while the cumarin has decreased the absorption of these nutrient 

 elements, it has not decreased it anywhere near the extent shown 

 by dihydroxystearic acid in the experiment cited. The third 

 column of figures gives the relative effect of cumarin absorption 

 of each nutrient element, and indicates that the phosphate and 

 potash absorptions were the more nearly normal of the three, 

 especially the phosphate absorption if the figures in the last column 

 are taken into account. This column gives the percentages of the 

 individual cumarin cultures which showed an absorption equal to 

 or greater than the corresponding culture without cumarin. 



In the second experiment this effect is clearly marked, the phos- 

 phate absorption being 91 per cent of the normal, as compared with 

 78 and 87 for the nitrate and potash, respectively. In this experi- 

 ment the total absorption of P 2 5 +NH 3 +K 2 was 1267 milli- 

 grams under normal conditions and 1077 milligrams with cumarin. 



While these figures indicate a somewhat more normal phosphate 

 absorption in the cumarin set than normal nitrate or normal potash 

 absorption, the figures are, nevertheless, not decisive enough to 

 enable one to say definitely that the antagonism of the phosphate 

 to cumarin, as shown in the growth of the plants, is due to this 

 cause alone. A rigid examination of the complete data does not 

 allow us to draw this conclusion without at the same time suggest- 

 ing the possibility of an external interaction between the lactone 



