"The stem ... of the Silver Birch is one of the masterpieces of Nature. Everything has been done to heighten its unrivalled brilliance. The horizontal peeling of the bark, making dark rings at irregular distances, the brown spots, the dark colour of the small twigs, the rough texture near the ground, and the exquisite silky smoothness of the tight white bands above, offer exactly that variety of contrast which makes us feel a rare quality like that smooth whiteness as strongly as we are capable of feeling it. And amongst the common effects in all northern countries, one of the most brilliant is the opposition of birch trunks in sunshine against the deep blue or purple of a mountain distance in shadow. At all seasons of the year the beauty of the birch is attractive and peculiarly its own. The young beech may remind you of it occasionally under strong effects of light, and is also very graceful, but we have no tree that rivals the birch in its own qualities of colour and form, still less in that air and bearing which are so much more difficult to describe. In winter you see the full delicacy of the sprays that the lightest foliage hides, and in early spring this tree clothes itself, next after the willow, with tiny triangular leaves, inexpressibly light in the mass, so that from a distance they have the effect of a green mist rather than anything more material. When the tree is isolated sufficiently to come against the sky, you may see one of the prettiest sights in Nature--the pure deep azure of heaven, with the silvery white and fresh green of the birch in opposition. And yet it is not a crude green, for there is a good deal of warm red in it, which gives one of those precious tertiaries that all true colourists value." Linnaeus named our common Birch _Betula alba_; but more than a century ago Ehrhart pointed out that there were two well-defined forms of the tree, which he proposed to separate as distinct species under the names of _B. verrucosa_ and _B. pubescens_. Hooker regards the first of these as the typical form, for which he properly retains the Linnaean name. It is distinguished by having the base of the bole covered with coarse, rough, and blackish bark, the _smooth_ leaves looking as though their base had been cut off, and the twigs warty. The _B. pubescens_ of Ehrhart appears to be a variety of Fries' _B. glutinosa_, which Hooker treats as a sub-species of _B. alba_. The bark at its base is smooth and white, its _downy_ leaves have a triangular base, and its twigs are free from warts. It sometimes assumes a bush-like form. The Dwarf Birch (_Betula nana_) is a distinct species, which occurs locally in the mountainous parts of Northumberland and Scotland. It is not a tree, but a bush, only two or three feet in height. Its firm-textured, round leaves have scalloped margins and short footstalks. [Illustration: _Pl. 16._ Birch--winter.]