For these reasons cases of atavism given without recording the
circumstances, or the precautions that guarantee the purity of the
fertilization, should always be disregarded. And moreover another proof
should always be demanded. The parent which yielded the seeds might be
itself a hybrid and liable to reversions by the ordinary laws of the
splitting up of hybrids. Such cases should likewise be discarded, since
they bring in confusing elements. If we review the long list of recorded
cases by these [176] strict methods of criticism very few instances will
be found that satisfy legitimate demands. On this ground it is by far
safer in the present state of our knowledge, to accept bud-variations
only as direct proofs of true atavism. And even these may not always be
relied on, as some hybrids are liable to split up in a vegetative way,
and in doing so to give rise to bud-variations that are in many respects
apparently similar to cases of atavism. But fortunately such instances
are as yet very rare.
After this discussion it would be bold indeed to give instances of
seed-atavism, and I believe that it will be better to refrain wholly
from doing so.
Many instances of so-called atavism are of purely morphologic nature.
The most interesting cases are those furnished by the forms which some
plants bear only while young, and which evidently connect them with
allied species, in which the same features may be seen in the adult
state.
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