Bentham and Hooker recognised only two species of birch as indigenous to the British Isles—namely, Betula alba, the common birch, and B. nana, an insignificant shrub which grows in the Scottish Highlands. Messrs. Elwes and Henry, however, in their great work give specific rank to each of the two forms of the common birch prevailing in this country. It is certainly strange that the difference between them has not received more attention from foresters, seeing that one is a far more valuable tree than the other. Whether they be permanent species or merely racial varieties matters not for practical purposes; but it matters much that the better kind be planted where conditions are favourable for it.

The commoner and less desirable of the two forms has been named B. pubescens, owing to the young shoots being clothed with down, sometimes so minute as to require a lens to show it. This and the habit of the tree are the only constant marks of distinction from the other form, which is named B. verrucosa, because the shoots, though shining and perfectly free from down, are studded with minute verrucÆ, or warts, easily discernible by the naked eye. I have found in southern Norway, where the two reputed species grow together, intermediate forms which are no doubt natural hybrids.

The two species are usually quite different in habit, the common birch (B. pubescens) never carrying the long pendulous branchlets which distinguish the silver birch (B. verrucosa). Moreover, the common birch does not usually attain the stature of the other, although Mr. Elwes mentions having measured one at Malborough 90 feet high, with a girth of 8 feet. This is the species which grows naturally over the greater part of Scotland, especially in the west and north. The distinctive downiness of the young twigs may have had its origin in the humid atmosphere and abundant rainfall of the regions where it most abounds. Geographically it enjoys a very wide range, extending farther north than any other tree—as far as latitude 71° near the North Cape—and reappearing in Iceland and southern Greenland, far within the limit of floating ice. Eastward it extends as far as Kamschatka, but it does not reach southward beyond the Alps, not being found in the Pyrenees or the Apennines, whereas the silver birch reaches down to Sicily.

Coming to the north-east of Scotland, to Strathspey, Deeside, and part of the basin of the Moray Firth, one finds a change in the aspect of the birch forest; for here, although the common birch still prevails on the wetter parts, the silver birch is dominant on the drained land and hill sides. It is there that the lady of the woods displays her true grace and it is hard to say whether she is more lovely in summer, when she waves her long green tresses in the breeze, or in winter, when the slanting sunbeams glint on the snowy stem, and the drooping branchlets appear like fine tracery against the sky. This is the true weeping birch so highly prized by landscape gardeners, and this is the species that should always be chosen for planting, provided the land is well drained, for it cannot stand damp feet with the same impunity as its cousin. The general rule is not difficult to remember that, whereas the common or downy birch will grow on almost any soil that is not actual swamp, the silver or weeping birch is very impatient of stagnant moisture.

Beautiful as are the birch woods of Strathspey (travellers to the North must have been charmed with those on both sides of the railway near Lochinsch Station), it must be confessed that the silver birch does not attain its greatest perfection in Great Britain. Individual trees may be found to compare pretty well with those in Continental woods; but the general average is not so good. I have not seen the birch forests of the Baltic provinces and Central Russia; those who have done so speak enthusiastically of them; but it is from no want of loyalty to the Birks of Aberfeldy that I have to admit that their bark has not the sheen nor their growth the free grace of their kindred in French, German, and Scandinavian forests.

Inseparably associated as the birch is with Scottish landscape, poets and painters have never wearied of honouring it. The late David MacWhirter got its beauty rather on the brain, and one turned rather tired of what became a mannerism in his work. Hamilton of Bangour never rang his quaintly iterative changes so tenderly as in his ballad, The Braes of Yarrow, the tragedy of a maiden with two lovers. The lovers fight, and one falls—

The comliest swain
That e'er pu'd birks on the braes o' Yarrow.

The survivor presses his court, trying in vain to persuade the girl to leave Tweedside and come to his home beside Yarrow.

Sweet smells the birk, green grows, green grows the grass—
Yellow on Yarrow's braes the gowan;
Fair hangs the apple frae the rock,
Sweet the wave of Yarrow flowin'.

"Flows Yarrow sweet?" she argues with him—

Flows Yarrow sweet? as sweet, as sweet flows Tweed;
As green its grass, its gowan as yellow;
As sweet smells on its braes the birk,
The apple frae its rock as mellow.

The late Professor Veitch laid finger on the only blot in this fair picture. Apples do not hang from rocks either in Tweedside or by Yarrow, but rowan berries do. It is a pity that Hamilton yielded so far to eighteenth century classicism as to introduce the conventional apple. The line would surely have run more smoothly—

"Fair hangs the rowan frae the rock."

But I have wandered away from the birch. Economically, this tree has hitherto been reckoned of indifferent value, though there is an inexhaustible demand for bobbins. Clogmakers, also, will make picturesque encampment among birches of suitable size, and pay a fair price for working up the stems.

Of the well-nigh imperishable bark no use is made in this country, except that chemists extract from it an antiseptic called pyrobetulin, used also in the preparation of glass for engraving. But Scandinavian farmers sheath their wooden houses with birch bark, which makes a durable, waterproof covering, with a beautiful silvery appearance very gratifying to eyes offended by the evil aspect of corrugated iron. In Russia, also, a fragrant oil is distilled from birch-wood, whence Russia leather derives its peculiar odour. Careful housewives should note that there is no kindling equal to birch bark, which blazes up almost as fiercely as celluloid.

Of late years, a new use has been found for birch, deserving attention from owners of land whereon this tree grows naturally. The small branches and spray are found serviceable in the preparation of steel plates, the price given at present being about 46s. a ton. The trees should be cut before the sap rises, else the bundles will lose weight in drying. In dealing with a birch wood for this purpose, the crop may be considered recurrent at short rotation; for numerous suckers arise from the roots after the tree is felled and grow very rapidly. It is to be noted with satisfaction that the well-nigh omnivorous rabbit cannot digest the young growths of birch; at least, it does not devour them wholesale.

The birch is very impatient of the shade of other trees. In its turn, although its delicate foliage might not be supposed to stop much light, its shade is very injurious to all other deciduous trees except the beech; a quality which causes one to wonder that such an experienced observer as P. J. Selby should have recommended it as a nurse for oak.[12] It is liable to be disfigured by the morbid growths popularly known as "witch's brooms." Authorities differ as to the cause of these fascinated bundles of twigs, some attributing them to the action of a fungus, Exoascus betulinus, others to the irritation brought about by a gall-mite (Eriophes rudis) attacking the buds. Probably both are contributory agents.

The Gaelic for birch is beith (pronounced "bey"), and may be recognised in numberless Scottish place-names, such as Drumbae, Auchenvey, Largvey, etc. The derivative beitheach (pronounced "beyoch"), signifying a birch wood, appears as Beoch in Ayrshire, Galloway, and Dumfriesshire.

Of exotic birches suitable for cultivation in the United Kingdom, there is a very complete collection in Kew Gardens. Among the North American species the black or cherry birch (Betula lenta) probably produces the best timber, but the most ornamental is the paper birch (B. papyrifera). The Japanese (B. maximowicsii) seems to promise better bulk than any other as a forest tree in this country.