The seeds of this one plant, when sown separately in my
garden, produced exclusively flowers with the small linear petals of
their parent. Although I had a hundred individuals bearing many
thousands of flowers, there was not an instance of reversion. And such
would [205] immediately have been observed, had it occurred, because the
hybrids between the cruciate and the normal flowers are not
intermediate, but bear the broad petals of the _O. biennis_.
We may now take up another phase of the question, that of the running
out of new varieties, shortly after their introduction into a new
country, or later.
The most widely known instance of this is that of the American corn in
Baden, recorded by Metzger and quoted by Darwin as a remarkable instance
of the direct and prompt action of climate on a plant. It has since been
considered as a reversion to the old type. Such reversions invariably
occur, according to Wallace, in cases of new varieties, which have been
produced quickly. But as we now know, such reversions are due to
spontaneous crosses with the old form, and to the rule, that the hybrids
of such origin are not intermediate, but assume the features of the
older of the two parents. In the light of this experience, Metzger's
observation becomes a typical instance of vicinism.
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