294 
RICHARD M. HOLM AN 
The results of these experiments, in which the behavior of the roots 
was followed closely by means of enlarged tracings made with a 
camera, were entirely uniform. I found no case in which the root 
showed any tendency to bend upward and grow in an oblique direc- 
tion. An account of one of the numerous experiments performed in 
this connection will be given here. Three seedlings of Vicia faba var. 
equina, whose roots were 2 to 2.3 cm. in length, were so placed that 
the roots were directed obliquely downward in moist air at an angle 
of 50° from the vertical. After sixty-four hours these roots were 
straight except for the curvature of the extreme tip and they were 
then so placed that the tips pointed directly downward. During the 
following seventy-seven hours, in spite of active growth, most careful 
observations made by means of enlarged camera drawings failed to 
show any trace of an upward curvature. No other change in the 
roots was noticeable except the increase in length and loss of the slight 
curvature of the root tips. Roots which were originally placed hori- 
zontally in air and which had reached the oblique position behaved in 
the same manner when they were turned until the tip pointed directly 
downward. Experiments with Lupinus albus yielded the same results 
as those with Vicia faba var. eqimia. Similar results were also ob- 
tained with roots which, after growth in the oblique position in air, 
were transferred to other media. Thus, of five roots of Vicia faba 
from 3.5 to 5.5 cm. long, placed at angles of from 30° to 50° in air, 
all, after having elongated from 4 to 5 cm. in the oblique position, 
grew straight ahead when the tips were directed downward and the 
roots surrounded by earth (in 2 cases) or loose moist sawdust (in 3 
cases). Similar results were obtained with five roots of the same 
species which were similarly treated except that they were placed 
horizontal in air at the beginning of the experiment. After forty-eight 
hours they had reached an oblique position from 30° to 50° from the 
vertical and had elongated in that direction for some time, but when 
the tips of these roots were directed downward no upward curvature 
of the root took place. These results not only indicate that these 
roots had not become plagiotropic but also that they did not possess 
any induced dorsiventrality such as not infrequently occurs in the 
case of rhizomes and of branches of subaerial stems. 
However in certain of Nemec's (1901, a, S. 91, 92) experiments 
he obtained results which certainly seem to indicate an assumption 
of plagiotropism by the roots with which he experimented. He 
