186 BOTANICAL GAZETTE [mace 
rheotropic have been sensitive to streams of the velocities given 
above. 23 
From the results obtained with these three water plants,we 
may infer that rheotropism is not a general phenomenon with : | 
such plants. Possibly it may not be found in -any water plant 
It would seem to be of distinct disadvantage for such plants to — 
be rheotropic in their roots. For only by insensitiveness tothe 
flow of water can the roots the most quickly find the solid sub | 
Stratum. — a 
Allium cepa was tested both in the bulb and in seedlings. e 
The bulbs used were of the variety known as “ multiplier.” They 
were suspended so that the lower end dipped slightly into the 
revolving dish of water. Three periods of revolution Were 
tried —g hours, 24 hours, and 37 hours—with the temperature 
ranging from 16° to 23°, most of the time being abort # 
The velocities of flow ranged from 100™ to 250™ per minute. 
The number of roots growing well was twenty-eight, and a 
were most of them 2 long when the experiment fiers a 
one of the three experiments eight roots bent positively 
negatively, and two grew vertically downward. In ad 
other experiments, one root bent negatively 90°, while the 
teen others grew in a vertical plane or showed no 
caused by the current of water. It would thus ee. 
Toots from the bulb of this variety of the onion are eithe! 
-Sitive or at most but very slightly sensitive rhe 
Twenty-three seedlings of the onion were tested 10 oe 
_ fanging from 75° to 600™ per minute, there being CO” 
revolution for 38 hours, at a temperature of 23.5 - Se 
ated from the vertical direction, though all grew well. 
mM asturtium officinale grows well with roots in sant 
suing a remarkably straight course downward. Forty 
5 with roots 1™ to 1.5™ in length had their roots Si”. 
continuous water stream for 45 hours, at a water l 
20.5° to 24.5°, velocity ranging from 100™ to goo™ 
___ All grew vigorously and vertically downward. 
_— Ricinus communis also grows straight roots in yi 
