LIBERATION OF OrGANIC Marrer By Roots oF GROWING PLANTS 37 
Tests for reducing substances were made with prussian blue in solutions 
ym. six sterile flasks in which maize plants had grown, using both the 
boiled and the boiled samples of the solutions as well as check nutrient 
lutions. These tests were made in solutions taken from plants at 
ferent stages of growth. Ten cubic centimeters of each solution was 
ed, and each received two drops of a 0.5-per-cent solution of phenol. 
ter the prussian blue was added, the tubes containing the solutions were 
owed to stand for twenty-four hours, at the end of which time notes 
re taken on the results. In each of the six tests the unboiled solution 
which the plant had grown gave a distinct reaction for reducing sub- 
ices. The boiled solution gave no reaction in three tests, while in 
> other three the result was rather uncertain. The check solution 
ve no definite test for reducing substances. 
Reduction of nitrates.— Since traces of ammonia were found in the 
rile solution which had surrounded the maize roots, it was thought 
ssible that thru the action of enzymes liberated by the plant this 
tmonia might have been formed from the nitrates in the nutrient solution. 
sts for nitrates were made, using sulfanilic acid and naphthylamine 
state. No positive results were obtained. As a further test the 
yhenylamine reagent was employed. ‘This reagent is considered to be 
sitive to nitrite 1 part in 32,000,000 and to nitrate 1 part in 44,000,000. 
e tests were made with a series of sixteen flasks and no positive results 
re obtained. 
Chis does not necessarily show, however, that reducing enzymes might 
; have been present, for the maize removed all the nitrates from the 
srient solution rather early in its development, and the liberation of 
ucing substances may not occur until after the plant has taken up most 
the nutrients necessary for its development, or the nitrites may be 
orbed by the plant. 
“he nitrites might not have been present because there were no nitrates 
n which they could be formed. The problem of supplying the nitrates 
| making the nitrite test was conducted as follows: Check flasks, 
lve in number, were prepared with the same nutrient solution that 
7; used for growing plants. A like number of test flasks were used 
ch contained solution from around the plant roots. One hundred 
ic centimeters was used in each flask, and the nitrate content was 
le equal in both check and test flasks. The flasks received phenol 
