1910] SCHREINER & SKINNER—ORGANIC SOIL CONSTITUENI 181 
experiments showed that the dihydroxystearic -acid interfered 
greatly with oxidation, and that this action was overcome to some 
slight extent in the center of the triangle but nearer to the nitrate 
end, thus showing perhaps that there is some correlation in these 
functions. 
SUMMARY 
The foregoing investigations have given the following results: 
1. An organic soil constituent, dihydroxystearic acid, hinders 
the growth of wheat plants, when this is present in solution in pure 
distilled water. 
2. The compound is also harmful in the presence of nutrient or 
fertilizer salts in all ratios of the fertilizer elements, P,O,, NH,, 
and K,O 
3. The compound is more harmful in those ratios of fertilizer 
elements not well suited for plant growth. 
4. The harmful effect of the compound is the lena in those 
ratios of fertilizer elements best suited for plant growth. 
5. The compound appears to be relatively much less harmful in 
the presence of fertilizers mainly nitrogenous than in the presence 
of fertilizers mainly phosphatic or potassic. 
6. The harmful compound modified greatly the removal of 
fertilizer elements from the solutions. The quantity of phosphate 
and potash removed was less in the presence of the compound, but 
the nitrate was not so influenced and on the whole the amount 
removed was even greater. 
7. The compound modified both amount and ratio of the three _ 
fertilizer elements removed from solutions, the ratio being higher 
in nitrogen, which was also the most efficient fertilizer element in 
decreasing the harmful effect, as above mentioned. 
8. The harmful compound has the additional effect of darken- 
ing the root tips, stunting root development, causing enlarged 
root ends, which are often turned upward like fish-hooks, and 
inhibiting strongly the oxidizing power of the roots. 
9. Those fertilizer combinations which tend to increase root 
oxidation are also the combinations which overcome the harmful 
effects to the greatest extent. 
Bureau oF Sorts 
U.S. DEPARTMENT OF AGRICULTURE 
Wasuincton, D.C. 
