stimulus required to bring the extra flow to the bracts, etc., being presumably the irritation induced by insect visitors. The next progressive state is for bracts to assume a more or less staminoid character. This is rare, but it has been noticed in Abies excelsa.* A substitution of anthers for bracts has been seen in Melianthus major, † concerning which Sig. Licopoli remarks that the flowers of chiefly the terminal racemes were imperfect, the summit of the floriferous axis bearing a tuft of perfect and imperfect anthers; the petals and the two carpels of the flower having been atrophied or arrested. Fig. 64 represents an involucral bract of Nigella, bearing an anther on one side of it; while Fig. 65, a, is that of a glume of Lolium perenne with an anther. That bracts should ever assume a pistilloid character is, à priori, still more unlikely, as being further removed from the central organ of the flower. Dr. M. T. Masters has, however, described a *Teratology, p. 192. + Bull. Soc. de Bot. Fr., Rev. bib., t. xiv., p. 253. Journ. of Lin. Soc. Bot., vol. vii., p. 121. malformed Lolium perenne, in which the flowering glumes had styles and stigmas (Fig. 65, a, b); the essential organs being absent, were replaced by a tuft of minute scale-like Fig. 64.-Involucral bract of Nigella, with anther (after 1 α b Fig. 65.-Glumes of Lolium, with anther and stigmas (after Masters). organs, some of which were prolonged into styliform processes, the sexual organs being otherwise suppressed. In a proliferous case of Delphinium elatum described and figured by Cramer,* the parts of the flowers were all metamorphosed into open rudimentary carpels. The axis was elongated and terminated above, in one case, by a similar abortive flower; in another, by an umbel of such flowers, every part of which was more or less carpellary while all the bracts on the prolonged axis, even those out of the axils of which the branches of the umbel sprang, were similarly made of open carpels. PROGRESSIVE CHANGES IN THE CALYX.-The sepals are usually homologous with the petiole of a leaf. This is obviously the case with the Rose, where the rudiments of the *Bildungsabweichungen, etc., heft. i., taf. 10. The figure is reproduced in Teratology, p. 126.. compound blades are retained (see Fig. 24, p. 93). In Pedicularis the blades are present as a minute fringe on the edge. In Ranunculus, Potentilla, etc., the broad base of the petiole is the only part present, for in abnormal conditions the blade may be borne above (Fig. 66). Similarly, in a gamosepalous calyx the teeth as a rule seem to be all that remain to represent the blades; for in Trifolium repens, when virescent, true unifoliate blades are developed on elongated pedicels, all arising from the border of the calyx-tube (Fig. 67), in which the teeth become pinnately nerved blades. Fig. 66.-Ranunculus with foliaceous sepal. Fig. 67.-Foliaceous calyx of Trifolium repens, with stipulate leaflets (after Baillon). The venation may in some cases assist in furnishing a clue as to the real nature of a part. Thus in Hellebore, as already seen (Fig. 61), the bracts are homologous with petioles, their venation being palmate, and not pinnate as in the divisions of the blades of the leaves. It is the same in the sepals, which are presumably therefore homologous with petioles as well. The sepals of Caltha resemble them in their venation, but in this plant the leaf is of a more primitive type, not being lobed, and has also a palmate venation. A similar difference between the venation of the sepals U and blades of the leaves is seen in Dipterocarpus and Mussanda (Fig. 68). Transitional states from a single to a double flower of Saxifraga decipiens, described and figured by M. C. Morren,* shows that the newly formed petals in the place of stamens, as also the normal petals of the flower, exactly correspond, both in shape and venation, with the cotyledons. Palmate venation thus simply represents a more primitive type; and, since flowers are constructed out of metamorphosed leaves-the vegetative being replaced by reproductive energies,-one naturally expects to find the calyx and corolla, which more nearly approach leaves in structure, to show arrested foliar conditions, as, e.g., are seen in palmate nervation and absence of blade or petiole, as the case may be. In Mussanda (Fig. 68) the teeth of the sepals are usually subulate and acuminate; but in the one foliaceous and subpetaloid sepal it is drawn out into a long petiolar form, which then expands into a palmately nerved lamina. The fact that a "tooth" is in this case prolonged into a "petiole " seems to imply that the sepal arises at once from the receptacular tube, which, therefore, one would infer to be axial. A somewhat analogous procedure is in the monstrous Trifolium, where the unifoliate blades, supported on long pedicels with stipular appendages as well, all arise from the border of the so-called calyx-tube (Fig. 67). There the inference would be the same, only that the receptacular tube is free from the Fig. 68.-Flower and leaf of * Les Bull. de l'Acad. Roy. de Bruxelles, t. xvii., p. i., p. 415. pistil, and not adherent as in the case of Mussænda. In both instances it will presumably be purely axial in character. Progressive changes in the calyx are not uncommon by its assuming a petaloid character. This is normal in some genera of Ranunculaceae, in Fuchsia, Rhodochiton, as well as in some members of the Incompleta, as in Mirabilis, Polygonum, Daphne, etc. Normally coloured sepals are most frequent in polysepalous genera. Abnormal colorisation, with or without any metamorphosis of the organ, is most frequent in gamosepalous flowers, as in the cultivated "hose-in-hose" varieties of Primula, Mimulus and Azalea. The calyx may be petaloid either wholly or in part only. In Mussænda (Fig. 68), one sepal only is normally sub-petaloid. Calceolaria has occasionally one or more sepals petaloid. Similarly Linaria (Fig. 69) and other instances might be mentioned. These condi with one sepal tions, brought about by cultivation, clearly Fig. 69.-Linaria, show the important part that high nourish- petaloid. ment plays as an external stimulus or factor in the production of colour. Staminoid sepals appear to be very rare. It is recorded by M. Gris that they have occurred in Philadelphus speciosus.' Pistiloid sepals are nearly equally as rare as staminoid. They have been observed by Mr. Laxton in double flowers of the Garden Pea (Fig. 70), in which there was a five or six-leaved calyx, some of the segments of which were of a carpellary nature, and bore imperfect ovules on their margins, the extremities being drawn out into sub-stigmatiferous styles.† *Bull. Soc. de Bot. Fr., t. v., p. 330. t Gard. Chron. 1886, p. 897; and Teratology, p. 302. |