92 Frederic Czapek. — The Anti-ferment Reaction in 
Lot D rotated for the same time, but with a period of seven minutes, and 
made therefore two revolutions. Lot A consisted of control roots placed 
vertically. The temperature was 20° C. Lots B, C, D were, of course, treated 
one after the other on the same klinostat. The reducing power of the pre- 
parations made from these roots decreased at the following rate (measured 
at intervals of five days) : — 
A 
B 
C 
D 
2-0 
2*0 
2-0 
2 0 CC * To 
i-6 
i *7 
i *7 
)) a 
1*2 
i*4 
1.4 
i *5 „ „ 
0.8 
1*2 
1*2 
I *3 ’} 95 
In another similar experiment the klinostat made one turn in twenty- 
five minutes, and the lots of seedlings were allowed to rotate for the follow- 
ing times : — B, for fifteen minutes : 
; C, thirty minutes ; D, sixty minutes ; 
A was again a control lot (temp. 20 
•3 c.). 
A 
B 
c 
D 
2-0 
2*0 
2-0 
2-0 cc. — AgNO s 
i -5 
1*7 
1-7 
r *8 5 ? 
i-i 
i *5 
i *5 
*■6 )} 99 
A third experiment with the same time of revolution (25') was 
designed to investigate the effects of more prolonged rotation. Lot A 
consisted of control roots ; B was rotated for three hours, C for six hours, 
D for twenty-four hours. Care was taken that the roots of the different 
lots were of the same age at the end of the experiment. 
A 
B 
c 
D 
2-0 
2-0 
2-0 
2-0 
i-6 
i-8 
1.8 
1-7 
1*2 
i *5 
i-6 
i *5 
o-8 
1-2 
1.4 
1-2 
Retardation in the oxidation of homogentisinic acid was therefore to 
be observed in every case. I may here briefly mention that the accumula- 
tion of homogentisinic acid can be demonstrated by direct titration with 
silver nitrate in roots rotated on the klinostat. We must conclude from 
these experiences that roots in rotation on the klinostat perceive the geo- 
tropical stimulus in the same time as roots standing vertically, and even that 
this stimulus lasts during the whole time of rotation. Now that it has been 
shown that the anti-ferment reaction occurs in roots placed horizontally 
after five to six minutes, the view I formerly held must be given up, viz. that 
the effect of the klinostat may be caused by the plant remaining in each 
position for too short a time to allow of perception. Why curvature does 
