To my surprise, the crossed plants when fully grown were
plainly taller and more vigorous than the self-fertilised ones. Bees
incessantly visit the flowers of this Linaria and carry pollen from one
to the other; and if insects are excluded, the flowers produce extremely
few seeds; so that the wild plants from which my seedlings were raised
must have been intercrossed during all previous generations. It seemed
therefore quite incredible that the difference between the two beds of
seedlings could have been due to a single act of self-fertilisation; and
I attributed the result to the self-fertilised seeds not having been
well ripened, improbable as it was that all should have been in this
state, or to some other accidental and inexplicable cause. During the
next year, I raised for the same purpose as before two large beds close
together of self-fertilised and crossed seedlings from the carnation,
Dianthus caryophyllus. This plant, like the Linaria, is almost sterile
if insects are excluded; and we may draw the same inference as before,
namely, that the parent-plants must have been intercrossed during every
or almost every previous generation. Nevertheless, the self-fertilised
seedlings were plainly inferior in height and vigour to the crossed.
My attention was now thoroughly aroused, for I could hardly doubt that
the difference between the two beds was due to the one set being the
offspring of crossed, and the other of self-fertilised flowers.
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