1902] THE RHEOTROPISM OF. ROOTS “485 
to a greater extent, the plants themselves, necessarily disturbed 
the flowing of the water. But the plants were not more than 
five in any aquarium, and hence were well separated from one 
another. Moreover, after the disturbance in passing one radial 
____ fow of plants, the stream had a full semicircle in which to com- 
Pose itself before meeting the other radial row. A practical 
___ test, made by suspending algal filaments to the roots and watch- 
___ ing their trailing, showed that the roots were met by a stream 
with a constant direction. 
_ Five plants of Elodea were used, and these produced eleven 
‘Toots in all. Two roots were in streams of a velocity of 628™ 
per minute, not allowing for the lagging; two in streams of 
345~ per min.; and one in a stream of 162™ per min. The 
_ fevolution continued without interruption for 60 hours, and the 
temperature of the water varied from 24° to 28°. These eleven : 
— showed considerable nutation, but none gave any curve in 
Response to the stream, the resultant position of each root being 
Weal | 
: o oe Pot uogeton perfoliatus four plants were used. The total 
ce of Toots formed was 48. They grew well in streams 
anging in velocity from 200 per minute to 628™ per minute. 
... . fvolution was maintained for 56 hours ina tempera- 
[76 fem 24° to 28°, but no curves resulted. The — 
mots were wholly indifferent to the stream. ee 
S$ aquatilis was represented by four individuals, = 
oe temperature of 24° to’ 28° in water with the roots: . 
ane n velocity of 18g°™ to 284™ per. minute. The roots - 
Stable, nutation, but no curves in response to the © 
Son through 4 ee 
but in oe arc often of 45° on each side of the vertical, 
i =]. atimeters during the course of the experi- | 
=o Clear. away any question that may arise at — 
: © the Suitability of the velocity of stream employed) — 
that all of the plants which have shown themselves _ 
eloped ten roots in all. The revolution continued for | oe 
nutation, like that in Elodea, consisted of oscilla- oe 
- *€sultant the roots advanced straight downward, oe 
