THE following chapter is devoted to the circumnutating movements of the
radicles, hypocotyls, and cotyledons of seedling plants; and, when the
cotyledons do not rise above the ground, to the movements of the epicotyl.
But in a future chapter we shall have to recur to the movements of certain
cotyledons which sleep at night.
[Brassica oleracea (Cruciferae)'.--Fuller details will be given with
respect to the movements in this case than in any other, as space and time
will thus ultimately be saved.
Radicle.--A seed with the radicle projecting .05 inch was fastened with
shellac to a little plate of zinc, so that the radicle stood up vertically;
and a fine glass filament was then fixed near its base, that is, close to
the seed-coats. The seed was surrounded by little bits of wet sponge, and
the movement of the bead at the end of the filament was traced (Fig. 1)
during sixty hours. In this time the radicle increased in length from .05
to .11 inch. Had the filament been attached at first close to the apex of
the radicle, and if it could have remained there all the time, the movement
exhibited would have
[page 11]
been much greater, for at the close of our observations the tip, instead of
standing vertically upwards, had become bowed downwards through geotropism,
so as almost to touch the zinc plate.
Pages:
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35