I think so, not from the evil which
manifestly follows from self-fertilisation, in many cases even in the
first generation, as with Viola tricolor, Sarothamnus, Nemophila,
Cyclamen, etc.; nor from the probability of the evil increasing after
several generations, for on this latter head I have not sufficient
evidence, owing to the manner in which my experiments were conducted.
But if plants bearing small and inconspicuous flowers were not
occasionally intercrossed, and did not profit by the process, all their
flowers would probably have been rendered cleistogene, as they would
thus have largely benefited by having to produce only a small quantity
of safely-protected pollen. In coming to this conclusion, I have been
guided by the frequency with which plants belonging to distinct orders
have been rendered cleistogene. But I can hear of no instance of a
species with all its flowers rendered permanently cleistogene. Leersia
makes the nearest approach to this state; but as already stated, it has
been known to produce perfect flowers in one part of Germany. Some other
plants of the cleistogene class, for instance Aspicarpa, have failed to
produce perfect flowers during several years in a hothouse; but it does
not follow that they would fail to do so in their native country, any
more than with Vandellia, which with me produced only cleistogene
flowers during certain years.
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