1902] THE RHEOTROPISM OF ROOTS 187 
twenty-three seedlings used none curved in the water stream. 
Ten roots were in revolving water for 20 hours, and thirteen 
other roots for 48 hours, in temperature from 19° to 24°, in 
velocities from 150° to 1200™ per minute, without one curve of 
any kind appearing. 
Quercus alba was hardly sufficiently tested. Only six seed- 
lings were tried, and no root of these was rheotropic. The 
duration of the experiment was 48 hours, the roots elongating 
I™ to 2™ in that period. The velocity of the current was 225™ 
to 600™ per minute. 
Cucurbita pepo and Citrullus vulgaris grow primary roots very 
Straight in an environment of water. Of the former species, 
forty-four seedlings have been used in five different experiments, 
| in which the water temperature ranged from 17° to 23, ,; te 
Nelocity of current from 150™ to 2000™ per minute, and the 
duration of the experiments from 1 3.5 hours to g days. In none 
of these Was any deviation from the vertical shown. 
In Citrullus vulgaris thirty-one seedlings were employed in 
ees ©xperiments, the water temperature in two being 21° and 
ny - third 24°. The revolution of water lasted in two for I 7 
: — for the third 24 hours. The velocity of current was 
oe cade to 1300" per minute. Only three slight positive 
‘“irves were formed. 
~ iM some cases was held constant throu 
