ertility, such
as happens when two distinct species are crossed, so that, in point of
fact, the offspring of these illegitimate unions correspond almost
precisely to hybrids.[370]

Mere variations of form arising from hybridisation or other causes
hardly fall within the limits of this work, though it is quite
impossible to say where variations end and malformations begin. There
are, however, two or three cases cited by Mr. Darwin[371] from Gallesio
and Risso to which it is desirable to allude. Gallesio impregnated an
orange with pollen from a lemon, and the fruit borne on the mother tree
had a raised stripe of peel like that of a lemon both in colour and
taste, but the pulp was like that of an orange, and included only
imperfect seeds. Risso describes a variety of the common orange which
produces "rounded-oval leaves, spotted with yellow, borne on petioles,
with heart-shaped wings; when these leaves fall off they are succeeded
by longer and narrower leaves, with undulated margins, of a pale green
colour, embroidered with yellow, borne on foot-stalks without wings.
The fruit whilst young is pear-shaped, yellow, longitudinally striated
and sweet; but, as it ripens, it becomes spherical, of a reddish-yellow,
and bitter."

=Sports or bud variations.=--These curious departures from the normal
form can only be mentioned incidentally in this place, as they pertain
more to variation than to malformation.

The occasional production of shoots bearing leaves, flowers, or fruits
of a different character from those found on the normal plant, is a fact
of which gardeners have largely availed themselves in the cultivation of
new varieties. The productions in question have been attributed to
various causes, such as cross-breeding, grafting, budding, dissociation
of hybrid characters, or reversion to some ancestral form, all of which
explanations may be true in certain cases, but none of them supply the
clue to the reason why one particular branch should be so affected, and
the rest not; or why the same plant, at the same time, as often happens
in Pelargoniums, should produce two, three, or more "sports" of a
different character.

These bud variations may be perpetuated by grafts or by cuttings,
sometimes even by seed. With reference to cuttings a curious
circumstance has been observed, viz., that if taken from the lower part
of the stem, near the root, the peculiarity is not transmitted, but the
young plant reverts to the characte