90 Frederic Czapek. — The Anti-ferment Reaction in 
three hours, but of roots stimulated for fifty minutes after two hours. This 
phenomenon may be explained by assuming a superposition of two 
processes. In the anti-ferment reaction, however, there seems to be no 
opposing process, so that the curve shows no striking maximum. 
The results of continued observation during the process of geotropic 
curvature are in harmony with the early occurrence of the maximal anti- 
ferment reaction and its prolonged persistence. The intensity of the 
anti-ferment reaction remains the same during the first beginning of 
the downward curvature, and it does not decrease before five hours have 
elapsed (at 16-17°), when the curvature is already finished. Since the 
root stays in the horizontal position about one hour, the anti-ferment 
reaction could not be expected to disappear in less than twenty-four 
hours, a supposition actually confirmed. Perhaps the result, that direct 
titration during the progress of the geotropic curvature shows after three 
hours no augmentation of the normal amount of homogentisinic acid, may 
seem to be a surprising one. But it is possible, on account of the very small 
quantity of substances to be estimated, that the method soon becomes 
useless. Perhaps also after the oxidation of the homogentisinic acid has 
been checked a regulative diminution in the production of homogentisinic 
acid takes place, so that even in the presence of the hindering antioxidase 
the amount of homogentisinic acid decreases a little. 
Further investigations on the significance of the anti-ferment reaction 
were made in reference to the geotropic induction at different angles to the 
vertical. When the roots are stimulated for thirty minutes no anti-ferment 
reaction can be observed at deviations of from i° to 6° from the vertical. 
The reaction becomes certain at an angle of 7 0 from the normal position. 
This therefore is the smallest stimulus able to cause the anti-ferment reaction. 
At a deviation of io° and a stimulation of thirty minutes a nearly maximal 
anti-ferment reaction can be produced, and the progress of the reaction is 
now the same for all angles from io° to 170°. Neither the horizontal 
nor the obliquely upward position have a stronger effect. The effect 
decreases at 176°, and at 179 0 the anti-ferment reaction is very little. The 
inverse vertical position never causes any anti-ferment reaction ; nor is any 
after-effect to be obtained in roots fixed in the inverse vertical position. 
I have shown elsewhere (12) that the maximal after-curvature is not to be 
obtained by stimulation in the horizontal position, but at positions of 
about 1 35 0 obliquely upwards, i. e. 45 0 above the horizontal. Therefore the 
inquiry whether the anti-ferment reaction does not after all show a maxi- 
mum effect at some angle of deviation was an interesting one. The 
method employed was the weakening of the effect by the shortening of the 
period of induction. If the induction is diminished to six minutes, at 
a deviation of io°, no distinct anti-ferment reaction can be observed, but 
a very distinct one at 170°. These positions had not differed from each 
