316 New combe. — Geo tropic Response at Various 
coleoptile) are among the most insensitive and aberrant of plants com- 
monly worked with. These two species have played leading roles in 
plant physiology far too long. With them one must continue the foregoing 
experiment twice as long as for the other species used. 
The results shown in the preceding table are decisive. They show 
the need of a critical examination of the method and results of Czapek 
by which he inferred a stronger response at 135° than at 90°. We have 
the alternative on the one hand of regarding Czapek’s method or the 
one employed here as faulty, or on the other of supposing that different 
tests, all fair, will lead to different conclusions as to the angle of inclination 
bringing the strongest geotropic response. On a later page of this paper 
evidence will be offered which is believed to indicate that the discrepancy 
in results by the two methods is due to the unreliability of one. It is 
difficult to see how the method used in this paper can be called unreliable. 
It is the method used by Czapek 1 himself to determine the inclination 
at which lateral roots give their strongest geotropic response. The number 
of stems and roots shown in the tables as remaining straight are of 
importance only in indicating that the experiments were not continued long 
enough to bring curves in all cases, and that there is considerable variation. 
Alternation at go° and 112*5°. — If* we accept the foregoing experimental 
proof of a stronger geotropic response at an inclination of 90° than at 
I 35° , we have still to determine whether the horizontal position is the 
one giving the strongest response. The following table shows the results 
obtained with a few seedlings alternated from 90° to 112*5°, conditions 
being the same as for the preceding series of experiments. The curves 
did not show till 8 to 10 hours after beginning the experiment. 
TABLE II. 
Showing results of stimzdation alternately at 112*5° an d 9 °° 
from the position of equilibrium. 
Plants. 
Total 
number. 
Curves 
caused 
by 90°. 
A T o 
curves. 
Curves 
caused by 
112.5 0 . 
Brassica alba , hypocotyl 
5 
5 
0 
0 
Helianthus annuus, ,, 
Zea Mays , coleoptile 
(White dent) 
7 
6 
1 
0 
6 
6 
0 
0 
Total stems 
18 
17 
1 
0 
Lupinus albus, primary root 
10 
9 
1 
0 
Helianthus annuus, „ „ 
2 
2 
0 
0 
Total roots 
12 
11 
1 
0 
1 Ueber die Richtungsursachen der Seitenwurzeln etc. Sitzungsber. d. k. Akad. d. Wiss., Math.- 
Naturw. Cl., civ, 1. Abt., 1895, p. 1216. 
