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. Yet the
pistil of each cabbage-flower is surrounded not only by its own six
stamens, but by those of the many other flowers on the same plant. How,
then, comes it that such a vast number of the seedlings are mongrelized?
I suspect that it must arise from the pollen of a distinct VARIETY
having a prepotent effect over a flower's own pollen; and that this is
part of the general law of good being derived from the intercrossing
of distinct individuals of the same species. When distinct SPECIES are
crossed the case is directly the reverse, for a plant's own pollen
is always prepotent over foreign pollen; but to this subject we shall
return in a future chapter.

In the case of a gigantic tree covered with innumerable flowers, it may
be objected that pollen could seldom be carried from tree to tree, and
at most only from flower to flower on the same tree, and that flowers
on the same tree can be considered as distinct individuals only in a
limited sense. I believe this objection to be valid, but that nature has
largely provided against it by giving to trees a strong tenden