1902] THE RHEOTROPISM OF ROOTS 265 
"were not taken in sufficient detail to show more than very gen- 
_ eralrelations. The results are these : 
TABLE II. 
__ EXPERIMENTS WITH AVENA SATIVA. Temperature in air 22° to 25°; period for each 
velocity from 10 to 17 hours, except in the case of 15 roots, where it was 30 hours. 
Total no. of roots | Flow per minute Percentages of curvatures 
96 25to 100™ | 46%¢=+, 51%=0, 1% 
57 100 to 300 Si. =+, l4 =0. 68 = 
58 300 to 2000 40 =+, 30 =, 30° = 
From this table it is evident that streams with a velocity 
below 100™ per minute do not bring responses in the majority 
: of individuals; and that velocities of 2000™ and below give 
~ Regative curves, these probably being merely mechanical. 
tis quite probable that velocities above 300™ per minute would 
sive a majority of Positive responses, but my notes do not set 
‘the approximate upper limit. 2 
The tests with Brassica alba show practically the same result 
nines Avena sativa. A velocity above 1000™ per minute will 
B¥ve, $0 far as my test goes, only vertical and negatively bent 
‘Dots, while a velocity between 600™ and 1000™ per minute will 
not bring @ positive response in one-third of the roots. s 
B 
TABLE III. 
: oe hdd BRASSICA ALBA, to show upper limit of speed calling forth § 
in air Period Flow per minute Percentage of curvatures 
it 
* [#5 024 hours} 50 to s00™ |syg=+, 138=0°, of=— 
> ‘|14 to 24 oo to 1000 (28 =-+, 50 =0,22 =~ 
es Ee Gad 1000 to 2000 | o =+, 50 =0,50 =~ — 
coe re fails to show the various angles assumed by the 
“rious velocities. In the rates between 100™ and 
ute, the angle was in more than half the roots 
oa and go», In 56 seedlings tested in a velocity below 
mute, the angle attained averaged less than 40°. _ In ‘ 
