fruit of _Opuntia_
and its allies is a dilatation of the flower-stalk. This is borne out by
the fruits of _Pereskia_, which bear leaves on their surface arranged
spirally; indeed, the fruits of _Pereskia Bleo_ are mentioned as
producing buds from their summits, in the same way as the _Opuntia_
just cited. _P. Bleo_ is said, by M. Delavaud,[179] to present this
anomaly as a constant occurrence. On the summit of the primary fruit,
arising apparently from the axils of the sepals, or of small leafy
bracts in that situation, are a series of fruit-like branches, which, in
their turn, are surmounted by others, even to the fourth generation.

The fruits of _Tetragonia expansa_ frequently have attached to their
side a secondary flower or fruit in such a position as to lead to the
inference that it springs from the upper portion of the peduncle which
is dilated to invest the true carpels. In other instances it is due to
an adhesion of the pedicel to the side of the fruit. In either case the
production of an adventitious bud might be considered as an illustration
of prolification of the inflorescence, though not as was supposed by
Moquin and others of axillary prolification.[180]

Buds have also been produced artificially on the surface of some of the
fruits in the construction of which the axis is supposed to share; thus,
the unripe fruits of some species of _Lecythis_ were stated by Von
Martius, at a meeting of the German Naturalists at Carlsruhe, to produce
buds when placed in the earth. The fruit of these plants is probably of
the same nature as that of the _Pomaceae_, and Baillon[181] succeeded in
producing buds on the surface of the inferior ovary of _Jussiaea_.

Some of the cases just mentioned have been considered to be instances of
prolification of the fruit, but the fruit has little to do with the
appearances in question.

=Formation of adventitious flowers and fruits within the ovary.=--This
generally arises either from substitution of a flower-bud for an ovule
or from prolification; there are certain cases, however, where the new
growth seems not to be either due to metamorphosis or to prolification
strictly.

The cut, fig. 94, represents a case where, in the dilated upper portion
of the ovary of _Sinapis arvensis_, two flower-buds were found
projecting from a raised central line, corresponding, as it would seem,
to the midrib, and not to the margins of the carpel. Similar cases have
occurred in _Nasturtium amphi