The examples given may suffice to convey a general idea of the
phenomenon, ordinarily called atavism by gardeners, and considered
mostly to be the effect of some innate tendency to revert to the
ancestral form. It is on this conception that the almost universal
belief rests, that varieties are distinguished, as such, from species by
their inconstancy. Now I do not deny the phenomenon itself. The impurity
of seeds and cultures is so general and so manifest, and may so easily
be tested by every one [199] that it cannot reasonably be subjected to
any doubt. It must be conceded to be a fact, that varieties as a rule
revert to their species under the ordinary circumstances of commercial
culture. And I cannot see any reason why this fact should not be
considered as stating a principal difference between varieties and
species, since true species never sport into one another.
My objection only refers to the explanation of the observed facts.
According to my view nearly all these ordinary reversions are due to
crosses, and it is for this reason that I proposed to call them by a
separate name, that of "vicinists." Varieties then, by means of such
spontaneous intercrossing sport into one another, while species either
do not cross, or when crossing produce hybrids that are otherwise
constituted and do not give the impression of atavistic reversion.
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