yal 
THE RHEOTROPISM OF ROOTS 179 
Juel? made use of the same apparatus that I had described in 
‘my abstra 
ct in 1896 —a revolving basin of water in which the 
roots of seedlings were immersed. He worked with only three 
plants, Zea mays, Vicia faba, and Vicia sativa. The first two 
were found unsatisfactory, being irregular in their response, 
- while the 
third was used for most of the results recorded. All 
three species were found to be positively rheotropic. No cer- 
tain evidence for negative curving was found. The positive 
response for Vicia sativa was shown in velocities of current from 
36™ per second down to 0.3™™ persecond. The maximum and 
minimum 
limits of velocity were not fixed. Juel experimented 
also with the location of the sensitive area, covering some root 
Ups with collodion caps and decapitating some roots. In both 
fases he obtained responses in the streaming water, and con- 
the 
des that the whole of the growing zone is sensitive ; whether 
foot-tip is sensitive was not determined. As to the nature 
of the stimulus inducing rheotropic bending, Juel could not 
‘Toots, the 
- When he placed thin cylinders of collodion over his 
foots curved as before. He concludes that the stimu- 
a May be pressure, but suggests that the collodion may have 
allowed a 
— Tt will 
1 
d nature of the stimulus. 
sufficient stream of water to pass through to give the © 
ulus as when the root is naked. oS 
be seen from the foregoing narration of work accom- 
II. METHODS. oe. 
ity of plants used in these experiments were seed- 
Seeds were planted in white pine (Pinus Strobus) 
wuungen iiber den Rheotropismus der Wurzeln. Jahrb. W 
