The other species--the Petty Spurge (_E. Peplus_)--is a smaller plant, seldom exceeding a foot in length, with an erect or decumbent stem branching at the bottom. The stem-leaves are oval or obovate, entire, shortly-stalked and placed alternately; and the floral leaves are cordate or broadly ovate. The flower-heads are small, surrounded by crescent-shaped glands with long points; and the carpels of the fruit have rough keels or wings. [Illustration: THE GREAT NETTLE.] Passing to the Stinging Nettles (order _Urticaceæ_), we have to deal with three herbs that are remarkable for the stinging hairs which clothe both leaves and stem. The leaves of all are opposite, and the flowers imperfect. The male flowers have four stamens, and a small, green perianth of four segments; while the females consist of an ovary with a tufted stigma, surrounded by a perianth of four segments the two inner of which are larger, or of two segments only. The fruit is a small, flattened nut, enclosed in the persistent perianth. The distinguishing characters of the three species are as follows: 1. The Small Nettle (_Urtica urens_).--An erect herb, from one to two feet high, with leaves and stem smooth with the exception of the stiff, stinging hairs. The leaves are thin, elliptical, deeply and regularly toothed; and the flowers are in unbranched axillary spikes which are shorter than the petioles, the males and females being intermixed. This is a common species, flowering from June to September. 2. The Great Nettle (_U. dioica_).--A dark green herb, from one to four feet high, more or less clothed with soft downy hairs in addition to the stiff, stinging ones. The lower leaves are ovate or cordate, coarsely toothed; and the upper ones narrower. The spikes of flowers are branched, longer than the petioles, in the axils of the leaves. The flowers are very similar to those of the Small Nettle, but the males and females are usually on separate plants. This is a very common species, flowering from June to September. [Illustration: CANARY GRASS.] 3. The Roman Nettle (_U. pilulifera_).--A coarse, erect plant, from one to two feet high, with stinging hairs more powerful than those of the other species. The leaves are ovate or cordate, deeply and regularly toothed. The male flowers are in clusters along the peduncles, which are often as long as the leaves; and the females are in globular heads at the top of stalks from half an inch to an inch in length. The heads of fruits are about a third of an inch in diameter, thickly covered with stinging hairs. This plant flowers from June to September. It is not so abundant as the other nettles, and is found principally in the neighbourhood of villages, especially in the eastern counties of England.