But to make
the case sure, he would raise plants from his supposed hybridised seed, and
he would find that the seedlings were miserably dwarfed and utterly
sterile, and that they behaved in all other respects like ordinary hybrids.
He might then maintain that he had actually proved, in accordance with the
common view, that his two varieties were as good and as distinct species as
any in the world; but he would be completely mistaken.
The facts now given on dimorphic and trimorphic plants are important,
because they show us, first, that the physiological test of lessened
fertility, both in first crosses and in hybrids, is no safe criterion of
specific distinction; secondly, because we may conclude that there is some
unknown bond which connects the infertility of illegitimate unions with
that of their illegitimate offspring, and we are led to extend the same
view to first crosses and hybrids; thirdly, because we find, and this seems
to me of especial importance, that two or three forms of the same species
may exist and may differ in no respect whatever, either in structure or in
constitution, relatively to external conditions, and yet be sterile when
united in certain ways. For we must remember that it is the union of the
sexual elements of individuals of the same form, for instance, of two long-
styled forms, which results in sterility; while it is the union of the
sexual elements proper to two distinct forms which is fertile.
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