[Illustration: FIG. 152.--Flower of St. Valèry apple, with sepaloid petals.]
M. Alph. de Candolle[295] describes an instance in _Primula Auricula_ in which the corolla had assumed the appearance of the calyx, but neither calyx nor corolla in this case possessed perfect stomata.
This malformation is much less common than the converse one of calycanthemy. Many of the recorded instances of so-called metamorphosis of the parts of the flower to sepals have occurred in monocotyledonous plants, or others in which the calyx and corolla are of the same colour, and constitute what is frequently termed the perianth; and as this is usually brightly coloured (not green) it is more convenient to group the metamorphoses in question under the general term Petalody, which thus includes all those cases in which the organs of the flower appear in the form of coloured petal-like organs, whether they be true petals or segments of a coloured perianth. As the morphological difference between the organs is one of position merely, there is little objection to be raised to this course, the less so as the term petalody merely conveys an idea of resemblance and not of absolute identity.
Petaloid coloration of the ordinary leaves, or of the bracts, is mentioned under the chapter relating to colour.
=Petalody of the calyx--Calycanthemy.=--As with the bracts, so the calyx in certain instances is naturally coloured, as in _Delphinium_, _Tropæolum_, and others. In _Mussænda_, _Calycophyllum_, _Usteria_, &c., one or more of the calyx lobes become enlarged normally. Considered teratologically, petaloid coloration of the sepals is either general or partial; in the latter case the nerves retain their green colour longest. There is in cultivation a variety of the primrose called _Primula calycanthema_, in which the upper part of the calyx becomes coloured, so that the flower seems to have two corollas placed one within the other; a similar thing happens in _Mimulus_, in which plant, as the calyx is permanent while the corolla is deciduous, the coloured calyx is a great advantage in a horticultural point of view. Morren[296] says that in order to produce the fine colour of the calyx of _Primula officinalis_ (var. _smaragdina_) the Belgian gardeners cut away the corolla in a very early stage, and that in consequence the colouring matter proper to the corolla is developed in the tube of the calyx, the edges of the limb remaining green, the middle of the limb being purple (_Primula tricolor_).