1912] SCHREINER &■ SKINNER— FERTILIZER SALTS 45 



We 



therefore, the interesting case of a toxic oxidizing 



overcome 



normal oxidative power of the root, accompanied by a 



element 



normal 



Discussion and summary 



In the foregoing experiments with cumarin, vanillin, and quinone, 

 the effects of these toxic substances on the development of wheat 

 seedlings was demonstrable by three criteria: 



1 



. By decreased green weight. 



2. By the morphological effects as shown by their general appear- 

 ance. Cumarin-affected plants have characteristic stunted tops, 

 broad, distorted leaves; vanillin-affected plants are less character- 

 istic, but show decreased growth of top and strongly inhibited root 

 growth; quinone-affected plants are tall and slender, with thin, 

 narrow leaves, in strong contrast to the cumarin-affected plants. 

 The substances show, therefore, a markedly different behavior in 

 detail, although all show a toxic effect in inhibiting growth. 



3- By decreased absorption of plant nutrients. The cumarin 

 depressed potash and nitrate removal from nutrient solution more 

 than phosphate; the quinone, on the other hand, depressed phos- 

 phate and nitrate more than potash; the effect of vanillin was not 

 determined in this regard. It might be interesting to mention, 

 however, that dihydroxystearic acid, which appears to act much as 

 vanillin did, depressed phosphate, and potash more than nitrate. 

 In this respect again the influence of the various harmful substances 

 was different. 



The various fertilizer salts acted differently in overcoming the 

 respective harmful effects of these toxic compounds. The mainly 

 phosphatic fertilizers were the most efficient in overcoming the 

 cumarin effects; the mainly nitrogenous fertilizers in overcoming 

 the vanillin effects; the mainly potassic in overcoming the quinone 



effect 



s. 



This different action of fertilizer salts on the toxic com- 

 pounds is also illustrated by the diagrammatic representations in 

 hg- 5 of the regions of greatest growth obtained in the various 



