182 BOTANICAL GAZETTE [MARCH 
tangential. To avoid the disturbing effect of the light and change 
- temperature, the experiments were, in most cases, conducted 
uta Gark room whose temperature was regulated to a variation 
of less than 2°. The lagging of the current was tested empit- 
cally by suspended and immersed particles, and found in al! 
parts of the basin toamount 
to less than I per cent. in 
velocities of less than 
thirty revolutions per min- 
ute. In the data givenim 
this paper this small re- 
tardation will be negie 
ted. 
Besides the revolving 
basin, a narrow wooden 
trough was sometimes 
used, The water for this 
was obtained from 4 by: 
drant, and was pass 
through a gas-heater be- 
fore being conducted © 
the trough. A fewexp® 
ments were made during 
the night in a brook flow 
é ds ei 
of Fic. 2.—A centrifuge and a preparation Boat mas dy of 
me seedlings of Brassica campestris raised ployed in the Sty b- 
ve the water. It will be seen that most of special parts of this ae 
the roots show rh i v v no . 
eotropic curves of 45° or over. wee 
> , ] Id best : 
wou 
em i] he 
the basin. 
tions of this pape 
Ill. GENERAL PHENOMENA. i 
The enon © Be 
- € general appearance and progress of the henom sell 
etropism in roots are as follows: When plants rheotrop! ~ 
