There are two Periwinkles (order _Apocynaceæ_), both of which have been introduced into Britain as garden flowers, but have become established as wild flowers in several parts. One of these--the Lesser Periwinkle (_Vinca minor_)--is moderately common, especially in the West, where it is often seen in thickets and other shady places, flowering during April and May. It has a trailing stem, from one to two feet long, rooting at the nodes; and short, erect, leafy, flowering branches. The leaves are opposite, narrow-elliptical, entire, and quite smooth; and the blue or violet flowers, which are about an inch in diameter, are solitary on short, erect stalks. The calyx is free, and deeply divided into five narrow segments; the corolla has a narrow tube, and five broad, spreading parts; there are five stamens, enclosed in the tube of the corolla; and the carpels are distinct at the base, but connected at the top by the single style. The other species--the Greater Periwinkle (_Vinca major_)--is a very similar plant, but its leaves are broader, with minute hairs on the margin; the calyx segments are also hairy at the edges; and the corolla is larger, with a broad tube. The Tooth-wort (_Lathræa squamaria_--order _Orobanchaceæ_) is a peculiar, fleshy, pinkish plant, to be found among decaying vegetable matter or at the roots of the Hazel, Elm and a few other trees. It is partly parasitic, deriving its nourishment from the roots of the trees to which it is attached, or sometimes obtaining its food partly or entirely from decaying leaves and stems. Its upright stem, which reaches a height of from five to ten inches, is covered with tooth-like, hollow scales, and bears a one-sided raceme of purple-brown flowers. This peculiar plant is not only a parasite on trees, but is also a carnivorous species, provided with the means of capturing and digesting very small animals, and a more detailed account of its form and habits will be found in our short chapter devoted especially to carnivorous plants. The Bugle (_Ajuga reptans_, of the order _Labiatæ_), is a very abundant flower in moist woods and pastures, blooming in May and June. It has a short root-stock, generally with creeping runners; and erect, smooth flowering stems from three to twelve inches high. At the base is a tuft of obovate, radical leaves, from one to two inches long, gradually narrowed into the stalk, with wavy margins; and on the stem are shorter leaves, with very short stalks, the upper ones often deeply tinged with blue or purple. The flowers are blue (occasionally pink or white), and are arranged in whorls of from six to ten in the axils of the upper leaves, the whole forming a leafy spike. They have a five-cleft calyx; a corolla with a short, erect, notched, upper lip; and a longer lower lip with three spreading lobes, the middle one of which is broader and notched. [Illustration: THE LESSER PERIWINKLE.]