321 
Angles of Inclination . 
showed, after 8 hours’ alternation, four individuals curving as though 
responding to the position above the horizontal, two curving as though 
responding to the position below the horizontal, and the other six straight. 
Three small potted plants of Fuchsia and three of Verbena were 
subjected to alternate stimulation, the stems of the former being respectively 
45 0 , 65°, and 70° from the horizontal, while those of the Verbena were 35 0 , 
45 0 , and 6o° from the horizontal. After 8 hours’ alternate stimulation only 
one stem, a Verbena , curved, and that was in the direction as though 
responding to the position above the horizontal. At the end of the 
alternation the plants were laid upon their sides at rest to see whether they 
were in a sensitive condition. After an hour and a half four of the six 
stems had curved geotropically. 
On the klinostat. — If stems and roots are not equally stimulated 
geotropically, at equal angles above and below the horizontal position, 
revolution on the klinostat with horizontal axis will, by summation of 
stimulation, cause curves. In making experiments to determine the 
question suggested, it is of the very first importance that the axis of the 
klinostat should be strictly horizontal, and the revolution should be 
uniform in every part of the course, since a very slight deviation in either 
direction will lead to erroneous conclusions. 
The klinostats used in my experiments revolved within the limits of 
once in 4 minutes, and once in 12 minutes. The temperature ranged 
between 17 0 and 25°, and the periods varied from 28 to 48 hours. A curve 
of a root toward the horizontal would indicate a stronger response from 
the position above the horizontal, while a curve away from the horizontal 
would indicate a stronger response from the position of the root inclined 
below the horizontal. Primary roots of Pisum sativum , to the number of 
nine, when adjusted 45 0 from the horizontal, showed three bending toward 
the horizontal, one away, and five straight. Twelve hypocotyls of Raphanus 
sativus showed one bending toward the horizontal, two away, and nine 
straight. Four hypocotyls of Brassica alba all grew without curving. 
Eleven coleoptiles of Zea Mays bent variously, but without any orientation. 
Two stems of Fuchsia showed no curves. 
These results certainly indicate that orthotropic roots and stems 
receive equal stimuli at equal angles above and below the horizontal. The 
curves which were formed in the foregoing experiments are regarded as 
autotropic, the plant having no external directive influence. The experi- 
menter knows that in the absence of directive influences such devious 
curves are not rare. 
