42 BOTANICAL GAZETTE [july 



general technique were the same as in the preceding experiments 

 with vanillin and cumarin, the concentration of quinone being 10 

 ppm. No analyses of the solutions were made in this experiment. 

 The duration of the experiment was from March 23 to April 4. 



The effect of the quinone on the development of the wheat was 

 in itself as definite, though perhaps not as characteristic, as the 

 effect of cumarin. The effect of the latter substance was to pro- 

 duce short, broad, irregularly developed leaves and stunted tops; 

 the effect of the quinone was to produce long, thin leaves, producing 

 tall, slender plants, so that at first glance the quinone in the con- 

 centration here used appeared to have had little effect on the growth 

 of the plants. Closer inspection, however, shows the plants to be 

 slender and weaker, although the leaves may be fully as long as the 

 normal leaves. The effect of quinone on plant growth, however, 

 is definitely shown by the decreased green weight. The root growth 

 is also affected. 



The most interesting feature of difference between the normal 

 and quinone sets of cultures, observable when both sets are arranged 

 in triangular form according to the composition of the culture 

 solution, is the apparent or real shifting of the greater growth 

 toward the potassium end of the triangle in the quinone set, accom- 

 panied by a generally better relative growth in the potash angle. 

 This observation would seem to show that the quinone effect was 



counterbalanced by the fertilizer combinations high in potash, 



whereas cumarin was undoubtedly affected by the phosphate 

 fertilizers, as shown, and vanillin as well as dihydroxystearic acid 

 by the mainly nitrogenous fertilizers. This effect was not antici- 

 pated, but might easily have been, inasmuch as quinone is a strong 

 oxidizing substance and potash salts are known from a previous 

 research 6 to be retarders of root oxidation, analogous to the opposite 

 effect of vanillin, a reducing substance overcome by nitrate known 

 to stimulate root oxidation. 



The green weights obtained at the end of the experiment bear 

 out this observation. The relative growth in the quinone set was 

 75 per cent of the normal. The chief interest, however, centers 



6 Schreiner, O., and Reed, H. S., The role of oxidation in soil fertility. Bull. 

 56, Bureau of Soils, U.S. Dept. Agr. 1909. 



