In many other cases, far from there being any
aids for self-fertilisation, there are special contrivances, as I
could show from the writings of C. C. Sprengel and from my own
observations, which effectually prevent the stigma receiving pollen
from its own flower: for instance, in Lobelia fulgens, there is a
really beautiful and elaborate contrivance by which every one of the
infinitely numerous pollen-granules are swept out of the conjoined
anthers of each flower, before the stigma of that individual flower is
ready to receive them; and as this flower is never visited, at least
in my garden, by insects, it never sets a seed, though by placing
pollen from one flower on the stigma of another, I raised plenty of
seedlings; and whilst another species of Lobelia growing close by,
which is visited by bees, seeds freely. In very many other cases,
though there be no special mechanical contrivance to prevent the
stigma of a flower receiving its own pollen, yet, as C. C. Sprengel
has shown, and as I can confirm, either the anthers burst before the
stigma is ready for fertilisation, or the stigma is ready before the
pollen of that flower is ready, so that these plants have in fact
separated sexes, and must habitually be crossed. How strange are these
facts! How strange that the pollen and stigmatic surface of the same
flower, though placed so close together, as if for the very purpose of
self-fertilisation, should in so many cases be mutually useless to
each other! How simply are these facts explained on the view of an
occasional cross with a distinct individual being advantageous or
indispensable!
If several varieties of the cabbage, radish, onion, and of some other
plants, be allowed to seed near each other, a large majority, as I
have found, of the seedlings thus raised will turn out mongrels: for
instance, I raised 233 seedling cabbages from some plants of different
varieties growing near each other, and of these only 78 were true to
their kind, and some even of these were not perfectly true.
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