38 : T. L. Lyon anp J. K. Witson 
to make the concentration 1 to 500, and were placed in the incubat 
at 23° CG. The next morning tests were made for nitrites, using the Grie 
reagent. No visible differences were apparent. A second test for nitrit 
was made after forty-eight hours. The result was positive in eve 
case. This test was repeated with the solution from another flask — 
which a maize plant had grown. While not so striking, the results. 
this case were also positive. Some tests were negative. A differen 
of NO; readings was not detectable in a colorimeter. 
Another series of tests for nitrate reduction was conducted, using 
eubie centimeters of the solutions in which maize plants had grown f 
periods of varying lengths and adding to this a small quantity of calen 
nitrate solution, at the same time introducing two drops of a 0.5-per-ce 
solution of phenol. Alpha-napthylamine and sulfanilic acid were us 
to test for the presence of nitrites, the solutions being allowed to sta 
for certain lengths of time varying from two hours to three days. St 
tests were made of the sterile solutions from eight flasks in which pla‘ 
had been grown, the solutions being taken for the tests within a few minu| 
after the flasks were opened. A sample of the solution from each of} 
flasks except one was boiled before being tested, and another sample ¥ 
not so treated. The check nutrient solution was tested in each ce 
Of the eight flasks tested, the unboiled solutions showed the presence 
nitrites in every case but one, the check solution showed the absence 
nitrites in six cases out of eight, and the boiled solution gave a react 
for nitrites in six tests but did not color so rapidly as did the unboi 
Apparently nitrate-reducing substances were usually. present in 
unboiled solutions in which the maize plants had grown, and boiling ; 
solutions failed to render these substances incapable of bringing ab) 
reduction of nitrates in the presence of phenol. t 
While the process of boiling did not completely prevent the lic 
surrounding the plant roots from effecting reduction of nitrates, it seelp 
to curtail its activity, as is indicated by the slower coloration of the rea } 
with the alpha-napthylamine and sulfanilic acid. The tests for reduiy 
substances by means of prussian blue, on the other hand, did not } 
any more reaction with the boiled solutions than with the checks. WI 
therefore, the operation of boiling produced some effects correspont 
to what might be expected from enzymes, there is some question af 
a} 
