Three days afterwards (i.e. 26th) the curvature had wholly
disappeared and the apex pointed perpendicularly downwards.
No. 5. Square attached on the 21st; on the 22nd decided
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though slight curvature from the square; on the 23rd the tip had curved up
above the horizon, and on the 24th was hooked with the apex pointing almost
to the zenith, as in Fig. 68.
No. 6. Square attached on the 21st; on the 22nd slightly curved from the
square; 23rd more curved; 25th considerably curved; 27th all curvature
lost, and the radicle was now directed perpendicularly downwards.
No. 7. Square attached on the 21st; on the 22nd a trace of curvature from
the square, which increased next day, and on the 24th amounted to a right
angle.
It is, therefore, manifest that the apex of the radicle of the oak is
highly sensitive to contact, and retains its sensitiveness during several
days. The movement thus induced was, however, slower than in any of the
previous cases, with the exception of that of Aesculus. As with the bean,
the terminal growing part, after bending, sometimes straightened itself
through the action of geotropism, although the object still remained
attached to the tip.
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