The Power of Movement in Plants | Page 6

sizes, and if the bending part of
the shoot had been distinctly hinged and could have been placed so as
to have formed one of the radii of the sphere. But even in this case it
would have been necessary afterwards to have projected the figures on
paper; so that complete accuracy could not have been attained. From
the distortion of our figures, owing to the above causes, they are of no
use to any one who wishes to know the exact amount of movement, or
the exact course pursued; but they serve excellently for ascertaining
whether or not the part moved at all, as well as the general character of
the movement.]
In the following chapters, the movements of a considerable number of
plants are described; and the species have been arranged according to
the system adopted by Hooker in Le Maout and Decaisne's 'Descriptive
Botany.' No one who is not investigating the present subject need read
all the details, which, however, we have thought it advisable to give. To
save the reader trouble, the conclusions and most of the more important
parts have been printed in larger type than the other parts. He may, if he
thinks fit, read the last chapter first, as it includes a summary of the
whole volume; and he will thus see what points interest him, and on
which he requires the full evidence.
Finally, we must have the pleasure of returning our [page 9] sincere
thanks to Sir Joseph Hooker and to Mr. W. Thiselton Dyer for their
great kindness, in not only sending us plants from Kew, but in
procuring others from several sources when they were required for our
observations; also, for naming many species, and giving us information
on various points. [page 10]
CHAPTER I.
THE CIRCUMNUTATING MOVEMENTS OF SEEDLING
PLANTS.
Brassica oleracea, circumnutation of the radicle, of the arched
hypocotyl whilst still buried beneath the ground, whilst rising above the

ground and straightening itself, and when erect--Circumnutation of the
cotyledons-- Rate of movement--Analogous observations on various
organs in species of Githago, Gossypium, Oxalis, Tropaeolum, Citrus,
Aesculus, of several Leguminous and Cucurbitaceous genera, Opuntia,
Helianthus, Primula, Cyclamen, Stapelia, Cerinthe, Nolana, Solanum,
Beta, Ricinus, Quercus, Corylus, Pinus, Cycas, Canna, Allium,
Asparagus, Phalaris, Zea, Avena, Nephrodium, and Selaginella.
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. As far as we could roughly ascertain by
measurements made with compasses on other seeds, the tip alone, for a
length of only 2/100 to 3/100 of an inch, is acted on by geotropism. But
the tracing shows that the basal part of the radicle continued to
circumnutate irregularly during the whole time. The actual extreme
amount of movement of the bead at the end of the filament was
nearly .05 inch, but to what extent the movement of the radicle was
magnified by the filament, which was nearly 3/4 inch in length, it was

impossible to estimate.
Fig. 1. Brassica oleracea: circumnutation of radicle, traced on
horizontal glass, from 9 A.M. Jan. 31st to 9 P.M. Feb. 2nd. Movement
of bead at end of filament magnified about 40 times.
Another seed was treated and observed in the same manner, but the
radicle in this case protruded .1 inch, and was not Fig. 2. Brassica
oleracea: circumnutating and geotropic movement of radicle, traced on
horizontal glass during 46 hours.
fastened so as to project quite vertically upwards. The filament was
affixed close to its base. The tracing (Fig. 2, reduced by half) shows the
movement from 9