I refer to the bud-variations of so many of
our cultivated varieties of shrubs and trees. Many of them are
cultivated because of their foliage. They are propagated by grafting,
and in most cases it is probable that all the numerous specimens [179]
of the same variety have been derived in this way from one primitive,
aberrant individual. We may disregard variegated leaves, spotted or
marked with white or yellow, because they are too inconstant types.
We may next turn our attention to the varieties of trees with cut
leaves, as the oakleaved _Laburnum_, the parsley-leaved vine and the
fern-leaved birch. Here the margin of the leaves is deeply cut and
divided by many incisions, which sometimes change only the outer parts
of the blade, but in other cases may go farther and reach, or nearly
reach, the midvein, and change the simple leaf into a seemingly compound
structure. The anomaly may even lead to the almost complete loss of all
the chorophyll-tissue and the greater part of the lateral veins, as in
the case of the cut-leaved beech or _Fagus sylvatica pectinata_.
Such varieties are often apt to revert by buds to the common forms. The
cut-leaved beech sometimes reverts partially only, and the branches
often display the different forms of cut-leaved, fern-like, oak-leaved
and other variously shaped leaves on the same twigs.
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