168 BOTANICAL GAZETTE [SEPTEMBER 
the center. The roots, on the other hand, are already showing 
differences. They are rather poor along the line having 8 parts 4 
per million of NH,. The upper and older part of the roots is 
dark, the newer portion is white and clear, but the tips are swollen. 
The general condition of the roots, as a whole, is a great deal 
better than in case of those in the boundary lines of the triangle. 
The condition of the roots on the line having 8 parts per million 
P,O,, and on the line having 8 parts per million K,O, are about 
the same as on the 8 parts per million NH, line. 
Farther within the triangle the general condition of the roots 
is much better. The solutions in cultures number 25, 32, 33, 34 4 
42, and 43 show by their roots that the harmful effect of the sub- : 
stance has been somewhat overcome: they are lighter than the 
others, in fact most of the roots, except the upper and older sec- 
tions, are white and clear, but the tips are still slightly swollen 
and somewhat bent. . 
Another property of the roots which is influenced by harmful 
bodies is that of root oxidation. It has been shown that plant 
roots possess a very appreciable power of oxidation, and that this 
power is stronger in good soils than in poor, or in their extracts, 
and that harmful bodies retard this oxidation, and beneficial | 
bodies augment it. Fertilizer salts were shown to increase root 
oxidation, and through this action a reduction in the quantity of 
the harmful body present was produced. 
Some further observations were made in connection with the 
present investigation in regard to oxidation and the effect of 
dihydroxystearic acid upon this function. The effect was % 
marked in the concentrations used, namely so parts per million,» 
that the roots at the end of the experiment were found to be almost 
wholly lacking in ability to oxidize aloin used as an indicator in the 
manner described in the publication referred to above. a 
oxidizing power was still possessed by the cultures in the interior of 
the triangle, where, as mentioned above, the growth was better 
than in other regions, although even here the power of oxidation 
was greatly impaired. Nevertheless, it is interesting to note that 
the condition which produced the best general development of 
the plants is closely associated with a power of root oxidatio® 
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