1910] SCHREINER & SKINNER—ORGANIC SOIL CONSTITUENT 163 
other factors reported in this paper. All of the harmful bodies 
which had been studied and presented in previous papers had a 
distinct influence on the roots, causing them in many cases to be- 
come stunted or swollen and darkened at the tips, or to show other 
physiological irregularities of the same kind as is exhibited by the 
roots in different extracts from infertile soils. It is, therefore, of 
interest to know further the influence which such altered root 
conditions would have upon the composition of the soil solution 
and the influence of added fertilizers. 
One of the bodies isolated from a number of unproductive soils 
is a definite crystalline body identified as dihydroxystearic acid 
melting at 98°-g9° C. It can be prepared by the oxidation of 
selaidic acid in the laboratory. In these experiments the dihy- 
droxystearic acid used had been prepared in this manner. The 
frequent occurrence of this body in such soils and its disappearance 
therefrom by processes which promote aeration or oxidation made 
this especially suitable for further study of its effects on plant 
development in relation to the concentrations of soil solutions or 
fertilizer application. 
The dihydroxystearic acid can be isolated from a soil containing 
it by treatment with a 2 per cent sodium hydroxid solution, and, 
after allowing the mineral material to settle, the alkaline extract is 
separated and made acid with a slight excess of acetic acid. The 
so-called humus precipitate which is thus formed is filtered off and 
the clear filtrate is shaken out with ether and the ether solution 
allowed to evaporate on the surface of a small quantity of water. 
The dihydroxystearic acid is left on the surface of the water, 
together with other impurities extracted by the ether. The 
impurities can be largely removed by heating the water to boiling, 
and filtering. Fig. x shows the effect of a solution of this nature 
on wheat seedlings when the material is dissolved in much water. 
The dihydroxystearic acid, when dissolved in a small volume of 
water and then cooled, crystallizes out in the form of small plates 
or leaflets arranged in radiating clusters. Fig. 2 shows the effect 
of the purified substance in various concentrations. The details 
of the method of isolating.and purifying will be found in the paper 
cited, 
