rsicifolia_, _Anagallis arvensis_,
_Gloxinia_, _Syringa persica_,[297] _Calceolaria_, _&c. &c_. In the
last-named plant one or more of the lobes of the calyx may frequently be
seen replaced by a slipper-like petal.

Among polysepalous plants petaloid sepals have been observed in
_Ranunculus auricomus_, _Rubus caesius_, _&c._ Fleischer also describes a
case of this kind in _Carum carui_.[298]

It will be seen from the above that in the majority of cases there is no
real metamorphosis or substitution of petal for calyx, but simply an
alteration in colour; nevertheless, a change in form may accompany a
change of colour: this happens especially if there has been any
displacement of organs. Thus, if, in an orchidaceous plant, a sepal be
displaced from any cause, or a petal be twisted out of its natural
position to occupy the place of an absent sepal, that petal will be
sepal-like in form, and _vice versa_.

=Petalody of the stamens.=--A petaloid condition of the stamens is one
of the commonest of all malformations. A large number of so-called
double flowers (flores pleni)[299] owe their peculiar appearance to this
circumstance.

It is necessary to distinguish carefully this petaloid development of
the stamens from the corresponding condition of the pistils, and from
that kind of doubling which is a result of multiplication of the
corolla, as in _Datura_, _Campanula_, _Primula_, &c. (flores duplices,
triplices, &c.), or from that produced by true median prolification
(flores geminati, &c.).

In cases of true petaloid development of the stamens there are usually
numerous intermediate forms between that of the true petals and that of
the perfect stamens; indeed, in _Nymphaea_, _Canna_, and in some other
plants, such a transition occurs normally. Petalody of the stamens may
occur either without material change in the flower or it may exist in
combination or in conjunction with an increased development of parts
(Multiplication), or with a similar change in the carpels, and it is
either partial or complete.

Among the flowers in which petaloid development of the stamens happens
most frequently may be mentioned those in which the calyx is normally
coloured, as in _Nigella damascena_, _Aguilegia_, and _Delphinium_.

M. Alph. de Candolle, in the 'Neue Denkschriften,' 1841, described and
figured a singular form of _Viola odorata_, known under the name of
"Bruneau," in Switzerland, in which the stamens are absent, and their
pl