ore or less
completely the appearance of petals, a singular appearance is afforded
by the presence of four wing-like processes emanating from the central
filaments, two on each side, so that the arrangement may be compared to
two sheets of paper folded in the centre and adherent in that situation,
though perfectly separate elsewhere, except sometimes at the top, where
they form a sort of hood. This change results from an imperfect petalody
of the anther; the two wings on each side of the central vascular cord
represent the front and back walls of an anther lobe, or rather of that
portion of the anther which, under ordinary circumstances, produces
pollen. In the malformed flowers no pollen is formed, at least in the
more complete states of the malformation, but the walls of the anther
lobe become preternaturally enlarged, and petaloid in texture and
appearance. This change occurs in some semi-double rhododendrons and
azaleas, in crocuses, and in a species of violet found at Mentone by Mr.
J. T. Moggridge.

There are numerous intermediate forms wherein the wing-like processes
may be traced all the way along the filament till they ultimately lose
themselves in the anther-lobes, with which they become continuous. In
some cases, as in _Crocus_ and _Rhododendron_, this is shown even more
clearly by the existence of two perfect pollen-sacs or quarter-anthers,
the remaining portions being petaloid and continuous with the dilated
filament. Not unfrequently these semi-petaloid stamens adhere to the
fronts of the petals, and then it appears, at a first glance, as if
three organs were stuck together, one in front of another, while in
reality there are but two.[305] (See _ante_, p. 35, fig. 12.)

[Illustration: FIG. 155.--Four-winged filaments of _Rhododendron_.]

The change in the anther, above alluded to, must not be mistaken for
that far more common one in which only a small portion of the anther
becomes petaloid, forming a sort of lateral wing or appendage to the
polliniferous portion, as happens normally in _Pterandra_, and is common
in some double fuchsias. In this latter instance there is but a single
wing, and the nature of the case is obvious.

Double flowers of _Orchidaceae_ generally arise from petalification of
the filaments, with or without other coincident changes. What makes
double flowers in this order the more interesting is the development, in
a petaloid condition, of some or all of those stamens which under
or