1902] THE RHEOTROPISM OF ROOTS 269 
in velocities between 50°" and 500™ per minute, but the largest 
angles also. The most of the curves in velocities below 50™ 
per minute are less than 30°, while the greatest angles are 
attained in velocities between 200° and 500™ per minute. 
To determine the effect of a very slow current on the direc- 
tion of growth of the roots of Raphanus sativus, three experi- 
ments have been carried out with the revolving water basin, 
divided as before into three concentric compartments, the roots 
being immersed in the two outer. The klinostats were adjusted 
to give one revolution in 32 minutes and one in 45 minutes, 
offering velocities ranging from 0.4™ to 2™ per minute. No 
difference in behavior of roots could be detected for the various 
velocities. The temperature of the air was held constantly at 
23°; the period of two experiments was 22 hours, and the other 
24 hours, Altogether seventy seedlings were used, giving thirty- 
‘four positive inclinations and three negative, while thirty-three 
foots grew straight. 
In the first place, it may be said that the roots of Raphanus 
“fe not disturbed, as are those of Brassica, by the very slow 
: — of water. It will be recalled that two-thirds of the 
pe the former grow irregularly in direction, in streams with 
| oa 6 below 2° per minute. The roots of Raphanus, which 
s ig designated above as neutral, pursued a vertical course 
downward, : 
ae Fg the second place, the fact should be emphasized that in - 
: i pi reams the character of the bend of the roots is dif- 
a that seen in the higher velocities. In the latter a 
S ent nae is concave toward the stream; in the former the 
| ie in, against the stream is either convex toward the stream, 
Ee cl 
How 2em ination is in a straight line. In very weak currents; a 
Vertical]. Per minute, the apex of the root for 2™™ or 3™ points - 
"sation, Sia ce. The angles attained by the roots of Raphanus © 
- the verti ay id low velocities ranged from 10 to _ : sige 
: - that nearly all the bending roots of the radish are 2 
