2 
RODNEY H. TRUE AND W. W. STOCKBERGER 
others. The peroxidase reaction was studied chiefly by means of 
the guaiac tincture followed by hydrogen peroxide. The guaiac test 
was supplemented by the test with pyrogallol and sometimes with 
gallic acid. 
The presence of an oxidase of the general type represented by the 
laccase of Bertrand and by the tobacco oxidase of Loew was easily 
demonstrated. This oxidase as found in the freshly expressed juice 
gave a reaction with guaiac tincture, pyrogallol and gallic acid. After 
precipitation with an excess of strong alcohol, the solution obtained 
on redissolving the precipitate in distilled water gave an intense re- 
action. Rough tests showed that in such solutions both the oxidase 
and the peroxidase reactions were inhibited by an exposure for four 
minutes to a temperature of 70° C. It appeared that this limit varied 
with the concentration and age of the enzyme solution. This inhibi- 
tion of the reaction made it clear that the causes of the color changes 
lay in something easily modified by heat, not in any of the more stable 
substances shown to be capable of bringing about like color changes 
in the guaiac tincture. It having been seen in preliminary tests that 
the oxidase and peroxidase reactions in the different organs of the 
plant differed widely in intensity, systematic data were sought on 
this point. 
In order to get evidence on the question of distribution from fresh 
materials, the reagents were taken to the field and applied to freshly 
cut surfaces of the growing plants. Here the order of intensity shown 
by the guaiac reaction agreed with that seen in the discoloration of 
the pulp. The most marked oxidase reaction was always seen in the 
more active younger parts of the plant. The fresh roots showed an 
almost complete lack of oxidase while the buds and petals were 
heavily loaded with it. The conclusion seemed justified that in this 
plant the intensity of the oxidase reaction increases from the base 
toward the summit of the plant. Similar tests for the peroxidase 
reaction showed clearly the presence in all parts of the plant of sub- 
stances causing this reaction and no marked difference in intensity 
seemed to characterize any special part of the plant unless a greater 
activity was seen in the buds and flower parts. 
The question immediately presented itself as to what particular 
tissues or substances contained the oxidases. When the guaiac 
tincture was applied to the cut surface of the growing plant, the drops 
of latex which instantly appear first gave the oxidase color reaction 
