With hybrids raised from the same seed-
capsule the degree of sterility is innately variable, so it is in a marked
manner with illegitimate plants. Lastly, many hybrids are profuse and
persistent flowerers, while other and more sterile hybrids produce few
flowers, and are weak, miserable dwarfs; exactly similar cases occur with
the illegitimate offspring of various dimorphic and trimorphic plants.
Altogether there is the closest identity in character and behaviour between
illegitimate plants and hybrids. It is hardly an exaggeration to maintain
that illegitimate plants are hybrids, produced within the limits of the
same species by the improper union of certain forms, while ordinary hybrids
are produced from an improper union between so-called distinct species. We
have also already seen that there is the closest similarity in all respects
between first illegitimate unions and first crosses between distinct
species. This will perhaps be made more fully apparent by an illustration;
we may suppose that a botanist found two well-marked varieties (and such
occur) of the long-styled form of the trimorphic Lythrum salicaria, and
that he determined to try by crossing whether they were specifically
distinct. He would find that they yielded only about one-fifth of the
proper number of seed, and that they behaved in all the other above
specified respects as if they had been two distinct species.
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