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 Tropæolum 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 Actæa 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 Tropæolum 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 laminæ. (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.

See Moquin-Tandon, 'El. Terat. Veg.,' p. 203. Engelmann, 'De Anthol.,' § 38 et seq.; tab. ii, figs. 8–14, Gilia; tab. v, 23–26, Senecio; tab. v, f. 1–13, Torilis; tab. iv, f. 3, Erysimum. 'Bull. Soc. Bot. Fr.,' vol. ii, 1855, p. 479, Primula sinensis. Giraud, 'Edinb. Phil. Magazine,' 1839, Antirrhinum. Jaeger, 'Act. Acad. Cæs. Nat. Cur.,' vol. xiii, 2, p. 1, tab. xli, Tropæolum. Bischoff, 'Lehrbuch,' 11, 2, p. 27, note, Tropæolum. Fresenius, 'Mus. Senkenb.,' ii, 35, tab. 4, fig. 5, Actæa. See also succeeding paragraphs and sections in Chloranthy, Virescence, &c.

Phyllody of the stamens happens less frequently than the corresponding condition in the neighbouring organs. The structure of the anther is so much removed from that of the leaf, that the change of the stamen from its ordinary condition to that of a leaf must be regarded as indicating a greater degree of perverted development than that which occurs in those cases where less highly differentiated organs, such as the sepals, petals, and pistils, are thus altered.[260]

In all cases it is desirable to ascertain, if possible, what parts of the stamen are thus transformed. In some Petunias the filaments are unchanged, but in place of the anther is a small lamina, representing precisely the blade of an ordinary leaf. Sometimes the connective only is replaced by a leaf. One of the most interesting cases of this kind that has fallen under the writer's observation was in Euphorbia geniculata, in which, in addition to other changes mentioned under prolification of the inflorescence, some of the stamens were partly frondescent, half the anther being perfect, the other half leaf-like. Another filament bore just above the usual joint three leaflets, two lateral ones, somewhat conduplicate, and a third central one, half anther, half leaflet.