Fig. 41.—Ligulate floret of wild Lettuce. kinds: viz. the ligulate, as exemplified in the floret of the wild Lettuce (Lactuca virosa) shown in fig. 41; and the tubular, as shown in a floret of the Cotton-thistle (Onopordium Acanthium) see fig. 42. All the British species of Compositæ have their florets either entirely of one of these kinds, or of the two mixed together; but some foreign genera have florets with two equal lips, cut
Fig. 42.—Tubular floret of the Cotton-thistle. into three or four lobes, as shown in a floret of Mutisia latifolia, at (e), fig. 46, p. 108. These florets are called bilabiate. It will be observed that in all these examples, as indeed, in all the flowers belonging to the order, that the pappus (b, in figs. 41 and 42), is always on the outside of the corolla, thus plainly indicating its connexion with the calyx.
The order Compositæ is a very large one, above seven thousand species having been named and described; and to assist the memory in retaining the names of this great number of plants, various means have been devised for dividing the order into sections and tribes. The principal botanists who have proposed means of arranging this order, are Cassini, Lessing, and lastly the late Professor De Candolle, in three volumes of his Prodromus published in 1840. But as the distinctions between the divisions proposed, lie in the difference found in the stigmas and pappus of the different genera, I have judged them too troublesome for my readers, as I am sure they are for myself, and I have preferred following the plan adopted by Dr. Lindley in his Elements of Botany, published in 1841, and dividing the Compositæ into four tribes; viz., the three originally proposed by Jussieu, and a fourth added by Professor De Candolle, containing the plants with bilabiate florets, which were either not known, or overlooked, by Jussieu. It may perhaps be necessary to add, that this arrangement forms the basis of the new one proposed by De Candolle, and that the principal difference consists in the subdivisions.
TRIBE I.—CICHORACEÆ.
Florets ligulate. Juice milky, narcotic.