let it be
observed that in the previous list no less than six well-known
varieties and several other unnamed varieties of the peach have once
suddenly produced perfect nectarines by bud-variation; and it would be
an extremely rash supposition that all these varieties of the peach,
which have been cultivated for years in many districts, and which show
not a vestige of a mixed parentage, are, nevertheless, hybrids. A
second explanation is, that the fruit of the peach has been directly
affected by the pollen of the nectarine: although this certainly is
possible, it cannot here apply; for we have not a shadow of evidence
that a branch which has borne fruit directly affected by foreign pollen
is so profoundly modified as afterwards to produce buds which continue
to yield fruit of the new and modified form. Now it is known that when
a bud on a peach-tree has once borne a nectarine the same branch has in
several instances gone on during successive years producing nectarines.
The Carclew nectarine, on the other hand, first produced half-and-half
fruit, and subsequently pure peaches. Hence we may confidently accept
the common view that the nectarine is a variety of the peach, which may
be produced either by bud-variation or from seed. In the following
chapter many analogous cases of bud-variation will be given.

The varieties of the peach and nectarine run in parallel lines. In both
classes the kinds differ from each other in the flesh of the fruit
being white, red, or yellow; in being clingstones or freestones; in the
flowers being large or small, with certain other characteristic
differences; and in the leaves being serrated without glands, or
crenated and furnished with globose or reniform glands.[669] We can
hardly account for this parallelism by supposing that each variety of
the nectarine is descended from a corresponding variety of the peach;
for though our nectarines are certainly the descendants of several
kinds of peaches, yet a large number are the descendants of other
nectarines, and they vary so much when thus reproduced that we can
scarcely admit the above explanation.

The varieties of the peach have largely increased in number since the
Christian era, when from two to five varieties alone were known;[670]
and the nectarine was unknown. At the present time, besides many
variet