Manito eBooks

in the direction of the window, so that we concluded
that the movement was heliotropic. But this was probably not the case, for
it was placed close to a north-east window and left there for 25 m., after
which time, instead of moving still more quickly towards the light, as
might have been expected, it travelled only at the rate of 12 m. 30 s. for
five divisions. It was then again left in complete darkness for 1 h., and
the point now travelled in the same direction as before, but at the rate of
3 m. 18 s. for five divisions.
We shall have to recur to the cotyledons of the cabbage in a future
chapter, when we treat of their sleep-movements. The circumnutation, also,
of the leaves of fully-developed plants will hereafter be described.
Fig. 11. Githago segetum: circumnutation of hypocotyl, traced on a
horizontal glass, by means of a filament fixed transversely across its
summit, from 8.15 A.M. to 12.15 P.M. on the following day. Movement of bead
of filament magnified about 13 times, here reduced to one-half the original
scale.
Githago segetum (Caryophylleae).


Pages:
28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52