THE RHEOTROPISM OF ROOTS. 
FREDERICK C. NEWCOMBE. 
: (WITH FIFTEEN FIGURES) 
: [Continued from p. 198.| 
, VELOCITIES EFFICIENT IN THE FORMATION OF CURVES. 
Ix my published abstract," already referred to, it was stated 
that definite relations exist between the velocity of flow and the 
‘sponse of the root. Juel? paid some attention to the same 
subject, finding that Vicia sativa grew generally with a negative — 
: “utve, or straight, in velocities. above 1800™ per minute; while 
= from that rate down to 1.8™ per minute the response was gener- 
Bea . Positive curve, Similarly with Zea mays (the variety is 
‘Rot given), the same au 
_Regative bend. As Juel points out, this does not neces- — 
= that the roots are either insensitive or negatively — : 
Hey are pr obably bent negatively or held vertical — 
mechanical push of the water. On the other hand, the c 
2 . of a stimulating current seems to have been approxi- 
Zea mays, but not for Vicia sativa, at the rate of 2™ per 
y own experiments to determine the limiting veloci 
wponse have been carried on with several plants, bu 
and the relation of response to a stimulus. Bor. Gaz. a2: 242 
iia oe 
mgen iiber den Rheotropismus der Wurzeln. Jahrb. Wiss. 
