The Strong-scented or Acrid Lettuce (_Lactuca virosa_) is moderately common on dry wastes. It is an acrid, glaucous, leafy and prickly plant, with a milky juice. Its erect stem grows to a height of three or four feet. Its leaves are spreading, obovate in form, with toothed margins, and bristly hairs on the under side of the midrib. The lower leaves are frequently marked with dark spots, and the upper ones have pointed auricles which clasp the stem. The heads of flowers are small, pale yellow, and arranged in a loose, spreading panicle. The bracts overlap, the outer ones being shorter, and the receptacle is flat. Each head contains only a few florets. The fruit is flattened, black, with a beak as long as itself and a pappus of many simple hairs. The flowers appear during July and August. Another Lettuce, known as the Prickly Lettuce (_L. Scariola_), is somewhat rare. It is really less prickly than the last species, but is equally tall, and flowers during the same months. Its leaves are erect, lanceolate, sagittate, with a wavy margin; and the upper ones clasp the stem. The fruit of this species is of a greyish colour, and has a beak of the same length. Two species of Sow-thistle (genus _Sonchus_) are included among our wayside Composites. They are erect, succulent plants, from two to three feet in height, with a milky juice, and either toothed or pinnatifid leaves. Their flower-heads are yellow, arranged in a corymb, and bloom during the whole of the summer. Each head is surrounded by several rows of overlapping bracts, and the receptacle is flat and pitted. The fruits are considerably flattened, without beaks; and the pappus consists of several rows of fine, silky, unbranched hairs. [Illustration: THE PRICKLY LETTUCE.] One species is known as the Sharp-fringed Sow-thistle or the Common Milk-thistle (_S. oleraceus_). Its leaves are sometimes deeply divided, but always more or less toothed; and the teeth often terminate in sharp prickles. The upper ones clasp the stem, and have spreading, arrow-shaped ears. The stem is branched and hollow; and the fruit is ribbed and transversely wrinkled. The second is the Common Sow-thistle (_S. asper_)--a very similar plant, but may be distinguished by its leaves, which are more spinously toothed, with _rounded_ ears. In this one the fruits are also ribbed, but they are not wrinkled transversely.