Bees and humble-bees fly from bud to bud, and carry the
pollen from one [187 ] sort to another, and separation by great
distances would be required to avoid this source of impurity.
Unfortunately the arrangements and necessities of large cultures make it
impossible to isolate the allied varieties from each other.
From a theoretical point of view the origin of these impurities is a
highly important question. If the breeders' atavism is due to crosses,
and only to this cause, it has no bearing at all on the question of the
constancy of varieties. And the general belief, that varieties are
distinguished from true species by their repeated reversion and that
even such reversibility is the real distinction of a variety, would not
hold.
For this reason I have taken much trouble in ascertaining the
circumstances which attend this form of atavism. I have visited a number
of the leading nurseries of Europe, tested their products in various
ways, and made some experiments on the unavoidable conditions of
hybridizing and on their effect on the ensuing generations. These
investigations have led me to the conclusion, that atavism, as it is
generally described, always or nearly always is due to hybridization,
and therefore it is to be considered as untrue or false atavism.
True atavism, or reversion caused by an innate latent tendency, seems
to be very rare, [188] and limited to such cases as we have spoken of
under our last heading.
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