Of the order _Rubiaceæ_ we shall include the common Field Madder (_Sherardia arvensis_), a little plant, varying from five to ten inches high, the minute lilac flowers of which may be seen from April to October. Its branched stems are often decumbent; and the little, narrow, sharply-pointed leaves, rough on the edges, are placed in whorls of from four to six. The umbels are very small, terminal, and surrounded by a leafy involucre that is divided into several lobes longer than the flowers. The corolla consists of an exceedingly slender tube, at the top of which are four spreading lobes; and the fruit is crowned by the five or six teeth of the calyx, which enlarges as the former ripens. The Field Knautia or Field Scabious (_Knautia arvensis_ or _Scabiosa arvensis_), shown on Plate VII, is very common on cultivated ground, particularly in corn-growing districts. It is a slightly-branched plant, from one to four feet high, clothed with stiff, bristly hairs. Its lower leaves are stalked, simple, narrow, and usually but little cut; and the upper ones sessile, broader at the base, and either coarsely toothed or deeply cut. The flower-heads are large, lilac, on long peduncles. The outer florets are much larger than the inner, and all have four-lobed corollas. The fruit is angular, and is surmounted by the eight or ten bristles of the calyx. This plant flowers from June to August. [Illustration: THE VENUS'S LOOKING-GLASS OR CORN BELLFLOWER.] Two of the Sow Thistles (order _Compositæ_) have already been noticed among the flowers of waste places (p. 179), and a third, known as the Corn Sow-Thistle (_Sonchus arvensis_), falls within the range of the present chapter, being a very common corn-field weed. It is an erect plant, from one to four feet high, with a hollow, angular stem, branched only towards the top. Its lower leaves are large, stalked, more or less divided into triangular, sharply-toothed lobes that are curved downwards; and the upper ones are sessile, less divided, with broad lobes which clasp the stem. The flower-heads are bright yellow, large, and arranged in a loose, terminal corymb. Their stalks and bracts are rough with stiff brown or black hairs; and the pappus of the wrinkled fruits consists of a dense mass of white, silky hairs. The plant blooms during August and September.