ORDER CVI.—DIPSACEÆ.—THE TEASEL TRIBE.
The principal genera belonging to this order are Dipsacus, the Teasel, and Scabiosa, the Scabious; to which may be added a pretty little annual called Knautia. The plants belonging to this order bear considerable resemblance to those included in Compositæ, as they consist of a head of florets seated on a common receptacle, which is chaffy, and surrounded by an involucre. The florets are also furnished with what may be called a double calyx, the limb of the inner part being cut into long teeth, and resembling the pappus of the Compositæ. In the genus Dipsacus, the most important plant is the Fuller’s Teasel (Dipsacus fullonum), in which the receptacle is raised in the form of a cone, and the chaffy scales are hooked, and so strong, that the flower-heads when dry are used for preparing broad-cloth. The leaves of this plant are opposite, and united at the base. The florets have a four-cleft corolla, and four distinct stamens; differing in this respect decidedly from the Compositæ, which have five stamens, the anthers of which are always united into a tube. Dipsacus sylvestris might be easily mistaken for a kind of Thistle; but the difference will be seen at once by examining the anthers of the florets. The Devil’s-bit Scabious, which is so called from the root looking as though a part had been bitten off, has the same kind of flower-head as the Dipsacus, but the receptacle is flat, and the involucre much smaller. In some of the species of Scabious, the florets of the outer ring resemble those of the ray in flowers of the Compositæ. The leaves of the genus Scabious are as variable as those of the genus Valeriana, scarcely two species being alike.
ORDER CVII.—CALYCEREÆ.
Obscure American plants, nearly allied to Compositæ.
ORDER CVIII.—COMPOSITÆ. (See Chap. VI. P. [98].)
Plants with heads of florets on a common receptacle, surrounded by an involucre. The florets are of three kinds, viz., ligulate, tubular, and bilabiate; the heads consisting sometimes entirely of florets of one kind, and sometimes with ligulate florets forming the outer ring, called the ray, and tubular flowers forming the centre, called the disk. The calyx continues on the ripe fruit, and its limb is frequently cut into a kind of fringe called the pappus. The fruit is of the kind called an achenium, that is, dry and bony, and continuing enveloped in the persistent calyx, but without adhering to it.