THE ROOT. 17 
now turn themselves in the direction inverse to centrifugal force, or 
towards the centre of the wheel. The rootlets, which, under 
ordinary circumstances, 
would bury themselves 
in the earth, and in the 
direction required by 
the laws of gravitation, 
in reality now point in 
the direction of the 
force which has taken 
the place of gravita- 
tion. 
This curious experi- — 
ment, carried out for 
the first time by Mr. J. 
A. Knight, a former 
president of the Royal 
Horticultural Society, 
has been repeated and 
modified in France 
by the ingenious na- 
turalist, Dutroch et. He Fig. 18.—Knight’s Vertical Wheel experiment. 
replaced the vertical wheel by a horizontal one, the force of 
gravitation acting constantly on the same points of the germinating 
») 
| 
| 4 
ee a 
i th an on 
== ———— 
Fig. 19.—Knight’s Wheel turning horizontally. 
seed; but as this seed is exposed at the same time to the action 
of centrifugal force, produced by the movement of the wheel, the 
e 
