But it should be repeated once more that most of the
highly cultivated plants, grown as vegetables, or for their fruit or
flowers, have so many crosses in their ancestry, that it seems better to
exclude them from all considerations, in which purity of [178] descent
is a requisite. By so doing, we exclude most of the facts which were
until now generally relied upon. For the roses, the hyacinths, the
tulips, the chrysanthemums always have furnished the largest
contributions to the demonstrations of bud-variation. But they have been
crossed so often, that doubt as to the purity of the descent of any
single form may recur, and may destroy the usefulness of their many
recorded cases of bud-variation for the demonstration of real atavism.
The same assertion holds good in many other cases, as with _Azalea_ and
_Camellia_. And the striped varieties of these genera belong to the
group of ever-sporting forms, and therefore will be considered later on.
So it is with carnations and pinks, which occasionally vary by layering,
and of which some kinds are so uncertain in character that they are
called by floriculturists "catch-flowers." On the other hand there is a
larger group of cases of reversion by buds, which is probably not of
hybrid nature, nor due to innate inconstancy of the variety, but must be
considered as pure atavism.
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