When the stamens of a flower suddenly spring towards the pistil, or slowly
move one after the other towards it, the contrivance seems adapted solely
to ensure self-fertilisation; and no doubt it is useful for this end: but
the agency of insects is often required to cause the stamens to spring
forward, as Kolreuter has shown to be the case with the barberry; and in
this very genus, which seems to have a special contrivance for
self-fertilisation, it is well known that, if closely-allied forms or
varieties are planted near each other, it is hardly possible to raise pure
seedlings, so largely do they naturally cross. In numerous other cases,
far from self-fertilisation being favoured, there are special contrivances
which effectually prevent the stigma receiving pollen from its own flower,
as I could show from the works of Sprengel and others, as well as from my
own observations: for instance, in Lobelia fulgens, there is a really
beautiful and elaborate contrivance by which all 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 raise plenty of seedlings. Another species of Lobelia, which
is visited by bees, seeds freely in my garden.
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