oliferous rose. Hip absent, sepals leafy,
stamens wanting, axis prolonged bearing supplementary flower, &c. (Bell
Salter).]

Proliferous roses have a special interest, inasmuch as they show very
conclusively that the so-called calyx-tube of these plants is merely a
concave and inverted thalamus, which, in prolified specimens, becomes
elongated (fig. 64) after the fashion of _Geum rivale_, &c.[127]
Occasionally from the middle of the outer surface of the urn-shaped
thalamus proceeds a perfect leaf, which could hardly be produced from
the united sepals or calyx-tube; a similar occurrence in a pear is
figured in Keith's 'Physiological Botany,' plate ix, fig. 12.

The change which the calyx undergoes when flowers with an habitually
adherent ovary become prolified, and wherein the calyx is disjoined from
the ovary, has been before mentioned, but it may also be stated that,
under such circumstances, the constituent sepals are frequently
separated one from the other, and not rarely assume more or less of the
appearance of leaves, as in proliferous flowers of _Umbelliferae_,
_Campanulaceae_, _Compositae_, &c.

As to the corolla, it was long since noticed that prolification was
especially liable to occur in double flowers; indeed, Dr. Hill, who
published a treatise on this subject, setting forth the method of
artificially producing prolified flowers, deemed the doubling to be an
almost necessary precursor of prolification;[128] but, though frequently
so, it is not invariably the case that the flower so affected is
double--_e.g._ _Geum_. If double, the doubling may arise from actual
multiplication of the petals, or from the substitution of petals for
stamens and pistils, according to the particular plant affected.
Occasionally in prolified flowers the parts of the corolla, like those
of the calyx, become foliaceous, and in the case of proliferous pears
fleshy and succulent. There is in cultivation a kind of _Cheiranthus_?
in which there is a constant repetition of the calyx and corolla,
conjoined with an entire absence of the stamens and pistils; a short
internode separates each flower from the one above it, and thus
frequently ten or a dozen of these imperfect flowers may be seen on the
end of a flower-stalk, giving an appearance as if they were strung like
beads, at regular intervals, on a common stalk. I have seen a similar
instance in a less degree in a species of _Helianthemum_.

The stamens are subject to various change