The Alder (_Alnus glutinosa_) is common in wet woods, and especially along the banks of streams in wooded valleys. Some of the mountain streams of the West of England, Wales, and Scotland, are bordered with almost continuous lines of Alder for miles together. This tree has a very dark grey bark, and the young branches are more or less triangular in form. The leaves are round, with a wedge-shaped base, and are green on both sides. They have very short stalks, are very blunt, and have a wavy, serrate margin. When very young they are hairy and sticky to the touch; hence the specific name of _glutinosa_. The catkins appear before the leaves, and are mature in March or April. The staminate catkins are pendulous, and much like those of the Birch; but the flowers have red scales and four stamens. The pistillate catkins are short and erect, and each flower has a fleshy scale within a reddish-brown, woody bract. The fruits are shed in the autumn, but the thickened woody bracts of the female catkin remain on the tree till, and even after, the flowers of the following spring are in bloom. Coming now to the order _Salicaceæ_, we have to deal with the Poplars, of which we have several species, all more or less common, and largely planted in cultivated ground. Our first example is the White Poplar (_Populus alba_), a large tree frequently seen in abundance in most woods. It has a smooth, grey bark, spreading branches, downy shoots and buds, and it throws off many suckers from its roots. The leaves are roundish, approaching a heart-shape, except those of the young shoots, which are divided more or less deeply into five lobes; and they are covered below by a white cottony down. The flowers are imperfect, and the male and female catkins, produced on different trees, are mature in March or April. The male catkins are three or four inches long, and each flower has from six to ten stamens, with red anthers. The female catkins are much shorter, and its flowers have divided stigmas, with long, narrow, yellow segments arranged like a cross. The ovaries ripen into capsules which split open in July, setting free seeds which are provided with cottony filaments; and the seeds often fall in such abundance as to almost completely cover the ground beneath the tree. The Grey Poplar (_P. canescens_) grows in similar situations, and flowers at the same time. Its leaves are roundish, with a waved and toothed margin, and are covered beneath with a slight coating of grey down. Those of the youngest shoots are more or less lobed. In this species the two stigmas are purple, wedge-shaped, and divided into from two to four lobes.