83 
Tropistic Movements of Plants . 
time in chloroform-water lose the power of reducing silver nitrate ; even 
small amounts of homogentisinic acid intentionally added to the preparation 
cannot be detected after some time. This is an enzyme action : pre- 
ventable by boiling the mixture, and to be observed even in filtrates from 
a Chamberland filter. The alcohol precipitate of this filtrate has the power 
of oxydizing homogentisinic acid in the same degree. We have here an 
enzyme (oxidase) capable of acting on homogentisinic acid, p-phenyl diamin 
+ a-naphthol, guaiacum, &c. It is clear that either the action of oxidase is 
somehow inhibited during geotropic stimulation, so that the homogentisinic 
acid, which is otherwise further acted on, disappears more slowly than under 
ordinary circumstances, and accumulates to a certain degree : or there must 
be temporarily a diminution in production of oxidase by the root-tip. 
If the latter were the case, it might be supposed that a mixture of an 
equal number of stimulated and non-stimulated root-tips would show the 
homogentisinic acid disappearing at a rate halfway between preparations 
derived entirely from stimulated and unstimulated roots. But the experi- 
ments I made show distinctly that such a mixed preparation does not 
differ in its behaviour from tests prepared entirely from stimulated roots. 
Therefore the existence of a specific retarding substance seems to be more 
probable. 
I demonstrated ( 9 ) that a mixture of eighty unstimulated root-tips and 
twenty stimulated ones gives the same rate of disappearance of reducing 
power as a preparation of stimulated root-tips. Further, it was shown that 
even four stimulated root-tips added to ninety-six normal root-tips gave 
a distinct retardation of the disappearance of the reducing power. The 
hindering effect therefore is an exceedingly strong one. Finally, it was 
discovered that the inhibitory substance can be destroyed by boiling, and 
can be isolated by filtration through a Chamberland filter, and precipitation 
by alcohol. The substance therefore has the properties of an enzyme, and 
may be characterized as an anti-oxydase, on account of its effect being 
contrary to that of the oxydase of the root-tips. This anti-oxydase has the 
property of other anti-enzymes, namely, that it is a strictly specific effect. 
In this way the anti-enzyme of geotropically stimulated hypocotyls of 
Lupinus has an effect on the oxydizing enzyme of a Lupinus root-tip, but 
not on the root-tip enzyme of Zea Mays or Cucnrbita. Between the 
oxydase and anti-oxydase of nearly related plants, therefore, a mutual 
action occurs, but not between enzyme and anti-enzyme of plants widely 
separated in regard to affinities ( 9 ). From these experiments on anti- 
enzymes it may be shown that the anti-enzyme produced in phototropic 
stimulation does not differ in any way from the geotropic anti-enzyme. 
It was established that the anti-oxydase is destroyed at 62° C, while the 
oxydase of the root-tip loses its power at 63 to 64° C. In a similar manner 
the anti-toxines lose their power at a lower temperature than the toxines, 
G 2 
