
No. 458.] GEOTROPIC RESPONSE IN STEMS. 79 
Jost (:02), after making various experiments, agrees with 
Stone in doubting the validity of Czapek's results. 
Just as this paper was ready to send to the publisher, there 
came to hand a preliminary report by Fitting (:04) in which the 
author states, among other results, that by a method somewhat 
similar to mine he has found the strongest geotropic effect when 
orthotropic plant members were placed in the horizontal position, 
that is, at 9o degrees from their position of equilibrium. 
Because of this division of opinion, and since, in all cases, the 
experimenters had been led to favor one of the two angles of 
deviation, 90 degrees or 135 degrees, it seemed that other angles 
might be neglected and the issue.drawn between these two. 
The present paper reports the results of a series of experiments 
made in the Botanical Laboratory of the University of Michi- 
gan under the direction of Professor Newcombe for the purpose 
of determining, in a considerable number of plants, at which of 
these two angles of deviation stems show the stronger geotropic 
response. Since the earlier work had dealt chiefly with seed- 
ling-roots and hypocotyls, the unbranched stems of actively 
growing young plants were selected as the material for use in 
most of these experiments. 
METHOD OF ALTERNATING STIMULATION. 
The two general methods used we shall call the “ Alternating 
Stimulation” and the “ After-effect” methods. It will be 
noticed that each differs somewhat from the methods of earlier 
workers. In all cases, except the first few experiments with 
Chrysanthemum which were made in the greenhouse where the 
plants were illuminated on all sides, the work was carried on in 
a dark-room whose temperature ranged from 20° to 24 €. (18.57 
C. in one case). 
It is evident that an orthotropic plant stem, if equally stimu- 
lated on opposite sides, will remain straight, but if unequally 
stimulated on the opposite sides, will become curved, and by the 
direction of its curvature indicate the stronger of the two 
stimuli. Since it was believed that the response of stems 
would be greater for stimulation in one of the two positions of 
