In other words it
seems probable that when the whitish variety arises a second time from
the red species, it is not at all necessary that it should exhibit this
same tendency to revert. Or to put it still in another way, I think that
we may suppose that a variety, which might be produced repeatedly from
the same original stock, would only in rare individuals have a tendency
to revert, and in most cases would be as absolutely constant as the
species itself.
Such a conception would give us a distinct insight into the cause of the
rarity of these reversions. Many varieties of shrubs and trees have
originated but once or twice. Most of them must therefore, if our
supposition is correct, be expected to be stable and only a few may be
expected to be liable to reversions.
Among the conifers many very good cases of reversions by buds are to be
found in gardens and glasshouses. They behave exactly like the whitish
currant. But as the varietal characters [169] are chiefly found in the
foliage and in the branches, these aberrations are to be seen on the
plants during the whole year. Moreover they are in some cases much more
numerous than in the first instance. The _Cryptomeria_ of Japan has a
variety with twigs resembling ropes. This is not caused by a twisting,
but only by a curvature of the needles in such a way that they seem to
grow in spiral lines around the twigs.
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