Fig. 55. Outline of piece of stick (reduced to one-half natural size) with
a hole through which the radicle of a bean grew. Thickness of stick at
narrow end .08 inch, at broad end .16; depth of hole .1 inch.
We succeeded better in ascertaining the force exerted transversely by these
radicles. Two were so placed as to penetrate small holes made in little
sticks, one of which was cut into the shape here exactly copied (Fig. 55).
The short end of the stick beyond the hole was purposely split, but not the
opposite
[page 75]
end. As the wood was highly elastic, the split or fissure closed
immediately after being made. After six days the stick and bean were dug
out of the damp sand, and the radicle was found to be much enlarged above
and beneath the hole. The fissure which was at first quite closed, was now
open to a width of 4 mm.; as soon as the radicle was extracted, it
immediately closed to a width of 2 mm. The stick was then suspended
horizontally by a fine wire passing through the hole lately filled by the
radicle, and a little saucer was suspended beneath to receive the weights;
and it required 8 lbs.
Pages:
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144