Centrifugal Force as Geo tropic Stimuli . 741 
Table I. 
No. of 
Helianthns annuus radicles. Temp, about 20° C. 
Results with short total periods. 
C t 
CT 
Exp. 
mg 
T 
(/+ n 
in. s. 
mg. t 
1 
3*24 
3-3i 
11 
0 
1-02 
2 
3*45 
3-17 
7 
30 
1-09 
3 
4-5i 
4'5 
7 
30 
1-00 
4 
5-45 
5-65 
7 
30 
0-96 
5 
5*47 
5-30 
7 
3° 
1.03 
6 
7*4 
7-97 
11 
0 
o-93 
7 
7.98 
7-94 
1 1 
0 
I-OI 
8 
9.7 
10-0 
1 1 
0 
0.97 
9 
io-39 
10-5 
1 1 
0 
0.99 
10 
10-52 
11-30 
5 
30 
o*93 
11 
1 1*4 
1 1-6 
5 
30 
0-98 
12 
13.2 
13.8 
7 
45 
0-96 
13 
15-2 
1 6-5 
1 1 
0 
0-92 
14 
16-4 
16-3 
15 
30 
I-OI 
15 
177 
177 
1 1 
0 
1-00 
16 
18-5 
18-2 
1 1 
0 
1-02 
17 
18-6 
19-0 
1 1 
0 
0-98 
18 
20-9 
20-85 
1 1 
0 
1-00 
CT 
Average value of = 0*9 9. 
mg. t 
The above results show that to a very near approximation — 1 or 
CT — mg. t., i. e. the stimulating force multiplied by the time of action must 
be the same in each direction if a radicle is to remain straight under the 
influence of two opposmg alternating stimuli . 
But it should be noted that the total period (/+ T) was never allowed 
to exceed 15 min. 30 sec. A large number of experiments, however, were 
performed with longer periods, but the results were quite out of keeping 
with those quoted above. It was usually impossible to trace a definite line 
of equilibrium across the box, so that any results that are given below are 
not very exact. And in many of the experiments the radicles all bent 
downwards, showing that the line of equilibrium is outside the box and 
further from the centre of rotation ; so that for equilibrium C must be 
greater than that at the upper edge of the box. 
The following experiments are quoted to show that the equation 
CT = mg. t does not hold if the total periods are long. In general the 
greater the centrifugal force and the longer the total period, the higher 
CT 
is the value of * 
mg. t 
3 E 
