88 Frederic Czapek . — The Anti-ferment Reaction in 
discovered by me are an expression of general disturbance of the normal 
state of organs under anomalous conditions. But we must admit that 
the connexion with the other processes of geotropic stimulus is, at present, 
entirely hidden from us. What can be made out is given in the following 
chapters. Speaking generally, it may be said that it is a question of 
changes demonstrable at a very early stage of the process, and having 
probably an indirect relation to the phenomena of perception. At present 
it is hardly to be decided whether important processes or collateral 
phenomena of the physiological act are to be seen in the anti-ferment 
reaction. At any rate, the results of my experiments show that the anti- 
ferment reaction is a very important method for investigating tropisms, and 
one capable of throwing valuable light on a variety of points. 
V. 
Hitherto the geotropic curvature of roots was principally used for the 
investigation of the anti-ferment reaction. And I shall accordingly in this 
paper deal especially with the phenomena of geotropism. 
First of all, it is of interest to know how long a period of stimulation 
in a horizontal position is needed for the appearance of the anti-ferment 
effect. The roots were kept horizontally for accurately measured periods 
of time (by means of a suitable apparatus), when they were placed 
vertically and underwent the anti-ferment test. Titrations were made, and 
the result is given in the following table (cubic centimetres of ^AgN0 3 
per 5 cc. filtrate), at intervals of five days. 
Time of induction, minutes : o' 3' 4' 5' 6' 
3 -o 
3 *o 
3 '° 
3 *° 
3-° cc. ^ AgN 0 3 
2-5 
2 -6 
2'5 
— 
2*7 55 55 
2*1 
2-1 
2-1 
2*1 
2 - 4 55 55 
i *3 
1-3 
1*2 
1-7 
2-2 „ „ 
0-9 
0.9 
0-7 
— 
2*0 „ „ 
The shortest period giving a distinct anti-ferment reaction by placing 
the roots horizontally at 17 0 C. can therefore be considered as six minutes. 
The limit is found at five minutes, nor was the limit changed by raising the 
temperature to 30°. But it is possible that the anti-ferment is not formed 
as an immediate result of stimulation, but rather by after-effect. Therefore 
I resolved to place the roots, after being geotropically stimulated, in the 
vertical position for one-half, one, two and more hours, and then to test for 
the anti-ferment reaction. But I could not detect even in this way any anti- 
ferment reaction after less than six minutes of geotropic introduction. On 
the whole it seems that, under any circumstances, at least five minutes’ 
