78 THE AMERICAN NATURALIST. (VoL. XXXIX. 
degrees, and least curvature in the stalks inclined less than 90 
degrees. 
Czapek ('95) took up the same line of experimentation as 
Bateson and Darwin, considering also the point which the other 
experimenters seem to have neglected, 7. e., the latent period of 
curvature in the various angles of deviation. His purpose was 
to determine at what angle of deviation it is possible to get the 
largest angle of geotropic after-effect, *the maximum reaction," 
for equally long induction periods. To eliminate specific differ- 
ences, a variety of plants was used: Lupinus, Faba vulgaris 
(Vicia faba), Phaseolus, Pisum, and Zea seedling-roots, hypo- 
cotyls of Helianthus, and matured internodes of Secale. The 
general result of Czapek's experiments is given in the statement 
that the extent of the angle of after-effect curvature increases 
steadily from the normal vertical position, reaching a maximum 
at about 45 degrees above the horizontal or 135 degrees from 
the normal, in the case of roots; 45 degrees below the hori- 
zontal or 135 degrees from the normal, in the case of stems ; 
then falls from that point to the inversely vertical position, 180 
degrees from the normal. The horizontal position is not, there- 
fore, according to Czapek, the one in which the maximum 
reaction takes place. 
In spite of his attempts in numerous experiments, even arti- 
ficially lengthened for the purpose of enlarging small time- 
differences, Czapek could detect no noticeable difference, as to 
time of beginning curvature, in stems inclined from 20 degrees 
to 150 degrees, but in those inclined less than 20 degrees and 
in those whose angles of deviation were between the optimum 
for geotropic response and the inverted position, 180 degrees 
deviation, found a very considerable delay in the beginning 
of response. 
Stone (: 00) experimented with dynamometers, measuring the 
after-effects of geotropic stimulation and found that in grass- 
nodes and in the roots of Micia faba, all experiments gave simi- 
lar results, indicating the horizontal position as that of greatest 
geotropic excitability. He further found the relationship between 
nodes at oblique angles and those horizontal to be proportional 
to the cosines of their angles. 
