Fig. 608.—Cirsium arvense: A the upper portion of a flower, the pollen (e) is being ejected; B part of the upper portion of the style with stylar-brush (b, c) and the stigmatic papillæ (d).
Fig. 609.—Leontodon autumnale: A ligulate flower; B extremity of the style with stylar-brush (a), stigma (b) and pollen-grains (c). C Centaurea cyanus.
Fig. 610.—Achillea millefolium.
The STYLE divides at the apex into two branches (Figs. [609], [610]), both of which generally bear on the inner surface two lines of stigmatic papillæ (Fig. [610] B, C) and being in shape, etc., very varied, are therefore employed as systematic characters.—The most important types are: A. The style is uniformly cylindrical; its branches are semi-cylindrical, long, and with long hairs, and finally bend backwards; the stylar branches bear slightly projecting stigmatic papillæ on the inner side. This form is characteristic of the Cichorieæ (Fig. [609] A B). B. The style is uniformly cylindrical; the branches are long, cylindrical or club-like, short, not rolled back, with fine hairs externally; the stigmatic lines do not reach beyond the centre, and do not meet together. Characteristic of Eupatorium, Petasites, Tussilago. C. The style is thickened beneath the stigmatic branches in the form of a knob, or very hairy (Fig. [609] C); the stigmatic lines reach as far as the apex of the branches and then converge; sometimes the stigmatic branches are united as far as the apex. Characteristic of the Cynareæ. D. The stylar branches are lanceolate, or linear, pointed; externally flat and thickly covered with hairs in the upper portion; the stigmatic lines cease where the hairs commence externally. Characteristic of Aster, Bellis, Inula, Dahlia, etc. E. The stylar branches are linear, with long, brush-like hairs at the apex, where they are either abruptly cut off or prolonged into a very hairy, conical appendage; the stigmatic lines are broad, reach as far as the brush-like hairs, and do not meet together (Fig. [610]). Characteristic of Senecio, Helianthus, Xanthium, Gnaphalium, Artemisia, Anthemis, and others related to these.
A ring-like nectary is found round the base of the style.
The thin-walled cypsela (Fig. [606]), with seeds fitting closely to the pericarp, has many different forms (smooth, ribbed, spined, etc.); its point of attachment generally lies at the lowest end but sometimes it is drawn obliquely up the side (Centaurea, etc.). The calyx, persistent on the apex of the fruit, has been described above. Some genera have two or three different forms of fruits in each capitulum.—The embryo is straight, with the radicle turned downwards, and without endosperm, but is rich in oil.
The variously flowered capitula, whose normal tubular disc-flowers have been changed to ligulate flowers, may be termed “double flowers.”
The relationship of the Compositæ to the Campanulinæ has been described above (page 561). The alliance with the Dipsacaceæ is more apparent than real. Similar capitate inflorescences also occur as the final stage in other lines of descent, as in Eryngium among the Umbelliferæ.