; and as I hold myself that, as regards many of the supposed
useless characters, this is the true explanation, it may be well to give
a brief sketch of the progress of knowledge in transferring characters
from the one category to the other.

We have only to go back a single generation, and not even the most acute
botanist could have suggested a reasonable use, for each species of
plant, of the infinitely varied forms, sizes, and colours of the
flowers, the shapes and arrangement of the leaves, and the numerous
other external characters of the whole plant. But since Mr. Darwin
showed that plants gained both in vigour and in fertility by being
crossed with other individuals of the same species, and that this
crossing was usually effected by insects which, in search of nectar or
pollen, carried the pollen from one plant to the flowers of another
plant, almost every detail is found to have a purpose and a use. The
shape, the size, and the colour of the petals, even the streaks and
spots with which they are adorned, the position in which they stand, the
movements of the stamens and pistil at various times, especially at the
period of, and just after, fertilisation, have been proved to be
strictly adaptive in so many cases that botanists now believe that all
the external characters of flowers either are or have been of use to the
species.

It has also been shown, by Kerner and other botanists, that another set
of characteristics have relation to the prevention of ants, slugs, and
other animals from reaching the flowers, because these creatures would
devour or injure them without effecting fertilisation. The spines,
hairs, or sticky glands on the stem or flower-stalk, the curious hairs
or processes shutting up the flower, or sometimes even the extreme
smoothness and polish of the outside of the petals so that few insects
can hang to the part, have been shown to be related to the possible
intrusion of these "unbidden guests."[42] And, still more recently,
attempts have been made by Grant Allen and Sir John Lubbock to account
for the innumerable forms, textures, and groupings of leaves, by their
relation to the needs of the plants themselves; and there can be little
doubt that these attempts will be ultimately successful. Again, just as
flowers have been adapted to secure fertilisation or
cross-fertilisation, fruits have been developed to assist in the
dispersal of seeds; and their forms, sizes, juices, and colours can be
show