1910] SCHREINER & SKINNER—ORGANIC SOIL CONSTITUENT 167 
and was especially striking in those sets where both triangles of 
cultures were grown simultaneously. In addition to the general 
appearance of the tops, the presence of this harmful body produces 
still other effects readily recognized by the investigator, and form- 
ing on the whole a better physiological indicator of the toxicity 
than the growth of tops, as has been well recognized by physi- 
ologists generally in conducting similar work. Reference is here . 
made to the action of the body on root condition and growth. 
The root being bathed by the solution, and being, moreover, the 
delicate mechanism of absorption, is often a more sensitive indi- 
cator than is the growth of the top. The most marked effects of 
dihydroxystearic acid on roots are strongly to inhibit their growth 
and to produce enlarged or swollen tips, which are frequently very 
dark in color and often turned back in the form of hooks. These 
phenomena are observed even when the injury is not so great as to 
kill the plants. This action of the body on the roots is influenced 
by the conditions of growth imposed upon the plant by the different 
fertilizer ratios. This is shown by the general notes taken on one 
of these sets one week after growth in the cultures had begun. 
All the plants in the solutions having no nitrogen appear to be 
dying. The roots are already dead, have made little growth, and 
are much discolored, the tips are dark and swollen and a large 
number turned upward. The tops have made some growth, some 
of the leaves are curled, but most are still fresh and green. 
The plants in the solutions containing no phosphate are similar 
to the above; the roots and tops are somewhat better, but still 
show an undoubted harmful action, the roots being dark and 
flimsy, tips swollen and often turned upward, the greater number 
being dead. 
The plants in the solutions on the potash base line are better 
than the two sets described above. The upper parts of the roots 
of these plants are dark, the lower sections that have recently 
grown out are white and clear, but the tips are still dark and swol- 
len, and many are turned upward. 
The plants in the interior of the triangle, where all three fertilizer 
ingredients are present, are fairly good, with no great difference 
noticeable at this stage, but showing somewhat better plants near 
