o mere outlines only are given here.

330. Sometimes the application of pollen to the stigma is left to
chance, as in dioecious wind-fertilized flowers; sometimes it is
rendered very sure, as in flowers that are fertilized in the bud;
sometimes the pollen is prevented from reaching the stigma of the same
flower, although placed very near to it, but then there are always
arrangements for its transference to the stigma of some other blossom of
the kind. It is among these last that the most exquisite adaptations are
met with.

331. Accordingly, some flowers are particularly adapted to close or
self-fertilization; others to cross fertilization; some for either,
according to circumstances.

_Close Fertilization_ occurs when the pollen reaches and acts upon a
stigma of the very same flower (this is also called self-fertilization),
or, less closely, upon other blossoms of the same cluster or the same
individual plant.

_Cross Fertilization_ occurs when ovules are fertilized by pollen of
other individuals of the same species.

_Hybridization_ occurs when ovules are fertilized by pollen of some
other (necessarily some nearly related) species.

332. =Close Fertilization= would seem to be the natural result in
ordinary hermaphrodite flowers; but it is by no means so in all of them.
More commonly the arrangements are such that it takes place only after
some opportunity for cross fertilization has been afforded. But close
fertilization is inevitable in what are called

_Cleistogamous Flowers_, that is, in those which are fertilized in the
flower-bud, while still unopened. Most flowers of this kind, indeed,
never open at all; but the closed floral coverings are forced off by the
growth of the precociously fertilized pistil. Common examples of this
are found in the earlier blossoms of Specularia perfoliata, in the later
ones of most Violets, especially the stemless species, in our wild Jewel
weeds or Impatiens, in the subterranean shoots of Amphicarpaea. Every
plant which produces these cleistogamous or bud-fertilized flowers bears
also more conspicuous and open flowers, usually of bright colors. The
latter very commonly fail to set seed, but the former are prolific.

333. =Cross Fertilization= is naturally provided for in dioecious
plants (249), is much favored in monoecious plants (249), and hardly
less so in dichogamous and in heterogonous flowers (338). Cross
fertilization depends upon the transportation of pollen; and th