In the
latter cases the radicles in growing downwards were deflected only a little
from the direction which they had followed whilst germinating in sawdust,
and they pressed lightly on the glass-plates (Fig. 21). Five of the most
distinct tracks are here copied, and they are all slightly sinuous, showing
circumnutation. Moreover, a close examination of almost every one of the
tracks clearly showed that the tips in their downward course had
alternately pressed with greater or less force on the plates, and had
sometimes risen up so as nearly to leave them for short intervals. The
distance between the extreme right and left positions of the radicle A was
0.7 mm., ascertained in the same manner as in the case of Phaseolus.
Epicotyl.--At the point where the radicle had protruded from a bean laid on
its side, a flattened solid lump projected .1 of an inch, in the same
horizontal plane with the bean. This protuberance consisted of the convex
summit of the arched epicotyl; and as it became developed the two legs of
the arch curved themselves laterally upwards, owing to apogeotropism, at
such a rate that the arch stood highly inclined after 14 h.
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