4 c BOTANICAL GAZETTE [JUL* 



were present, 5 and so should be a body which would behave much 

 like dihydroxystearic acid. 



In the present experiment with vanillin here recorded, the same 

 number of cultures (66), containing all the fertilizer combinations 

 possible in 10 per cent stages, was used as in the experiment with 

 the dihydroxystearic acid and cumarin. The concentration of 

 vanillin used was 50 ppm. The duration of the experiment was 

 from March 7 to March 19. The solutions were changed every 

 three days as in the cumarin experiment already described, but no 

 analyses of the solutions were made in this case. The green weight, 

 however, was recorded. 



The effect of the vanillin was not so marked on the tops as on 

 the roots, although in the regions of better growth this also was not 

 very prominent. The general appearance of the plants resembles 

 the effect produced by dihydroxystearic acid much more than the 

 effect produced by cumarin under the same circumstances. The 

 region of greatest growth appeared also, as in the case of dihy- 

 droxystearic acid, to be shifted toward the nitrogen end of the 

 triangle. The plant growth was 84 per cent of the normal as an 

 average of all the cultures. 



For the present purpose, however, the growth in the cultures 

 respectively high in phosphate, nitrate, or potash is of paramount 

 interest. This grouping of the results obtained on the green 

 weights at the termination of the experiment is shown in fig. 3* 

 The relative growth in the cultures having 50 per cent and more of 

 phosphate was 85 per cent of the growth without the vanillin; for 

 the cultures mainly nitrogenous it was 88; and for the cultures 

 mainly potassic it was 82. It will be observed that the vanillin 

 depressed the growth least in the cultures high in nitrate, a result 

 in harmony with previous observations on the toxicity of vanillin 

 and in harmony with the action of dihydroxystearic acid. Both 

 of these substances have reducing properties; that is, they are 

 themselves readily oxidized ; both have an inhibiting effect on root 

 oxidation and on root growth generally; both are overcome by 

 the fertilizer combinations which increase root oxidation to the 

 greatest extent . It was consequently thought to be of interest to 



s Schreixer and Reed, Jour. Amer. Chem. Soc. 30:85. 1908. 



