=Phyllody of the corolla.=--The petals also are frequently replaced by leaves, though in many of the recorded instances the change has been one of colour only; these latter are strictly cases of virescence. M. Seringe[259] speaks of a flower of _Peltaria alliacea_ in which the calyx was petal-like, while the corolla was leafy as if there had been transposition of the two organs, a very rare, if not unparalleled, instance. In a flower of _Campanula Medium_, provided, as is often the case, with a double corolla, the outer corolla was slit down on one side, the edges of the cleft being leafy. [Illustration: FIG. 133.--Sepals and petals to leaves. _Geranium_.] The frondescent petals are very often completely disjoined, as in _Verbascum nigrum_, and _Lonicera Periclymenum_, in which, moreover, median prolification generally coexists. In the case of _Tropaeolum majus_, the ordinary leaves of which are peltate and orbicular, the petals when frondescent have not the peltate arrangement, but are spathulate, and provided with very long, narrow stalks, so that, in some cases, they are, more properly speaking, enlarged virescent petals than true leaves; in other instances, however, the arrangement of the veins is more like that of the true leaves than that of the petals. As might be expected, frondescence of the petals is frequently accompanied by other changes of a similar nature in other parts of the flower, and sometimes by the abortion of the sexual organs. Thus, in _Actaea spicata_, as observed by Fresenius, the petals were replaced by true petiolate, palminerved, lobed leaves, the stamens and pistils being abortive. In _Ranunculus_ the leaves that appear in the place of the petals have no scale at their base, and in _Tropaeolum_ the calyx (or receptacle) is free from the usual spur. The absolute frequency of this occurrence seems to be greatest in those flowers which are normally polypetalous. The petals of these flowers, as a general rule, are more like the leaf-sheaths than the leaf-blades as to their venation, hence it would seem that the phyllomorphic condition in these petals is a manifestation of a greater degree of organizing force than that which occurs in those cases where the petals are normally present in the form of contracted blades or laminae. (See the remarks in the preceding section.) Frondescence of the petals has been observed most frequently in the following cases; some, perhaps, were cases merely of virescence, q. v.; see also under Chloranthy, Prolification.