Pistillody of the stamens.=--This change whereby the stamens assume more
or less the appearance of pistils is more commonly met with than is the
metamorphosis of the envelopes of the flower into carpels. In some cases
the whole of the stamen appears to be changed, while in others it is the
filament alone that is altered, the anther being deficient, or
rudimentary; while, in a third class of cases, the filament is
unaffected, and the anther undergoes the change in question. In those
instances in which the filament appears to be the portion most
implicated, it becomes dilated so as to resemble a leaf-sheath rather
than a leaf-stalk, as it does usually.

One of the most curious cases of this kind is that recorded in the
'Botanical Magazine,' (tab. 5160, f. 4) as having occurred in _Begonia
frigida_ already alluded to, and in which, in the centre of a male
flower, were four free ovoid ovaries alternating with as many stamens.
In the normal flowers of this plant, as is well known, the male flowers
have several stamens, while in the female flowers the ovary is strictly
inferior, so that, in the singular flower just described, the perianth
was inferior instead of being superior, as it is usually. It should be
added also that the perianth in these malformed flowers was precisely
like that which occurs ordinarily in the male flowers.

[Illustration: FIG. 161.--Supernumerary carpels in the orange, arising
from substitution of pistils for stamens.]

In some varieties of the orange, called by the French "bigarades
cornues," the thalamus of the flower, which is usually short, and
terminated by a glandular ring-like disc, is prolonged into a little
stalk or gynophore, bearing a ring of supernumerary carpels. These
carpels are isolated one from another, and are formed by the
transformation of the filaments of the stamens.[336]

The additional carpels in the case of the apple of St. Valery, in which
the petals are of a green colour, like the sepals, are by some
attributed to the transformation of the stamens into carpels. These
adventitious carpels frequently contain imperfect ovules and form a
whorl above the normal ones. (See _Pyrus dioica_ of Willdenow.)[337] A
similar change occasionally happens in the stamens of _Magnolia
fuscata_, while in double tulips this phenomenon is very frequent, and
among them may be found all stages of transition between stamens and
pistils, and many of the parts combining the characters of both.[338]