If the Oak and the Beech contend for the rank of king, there is no doubt as to the right of the Birch, clad as she is in cloth of silver, adorned with emeralds, or with "patines of pure gold," to the title of queen of the woods. Often has this tree roused the enthusiasm of both the artist and the writer; but, useful as it has been in other ages, and as it still is in other lands, it is now mainly for its aesthetic value as part of some of our most beautiful landscapes that we treasure it.
The very name Birch, in its identity with "bark," "barque," or "barge," suggests the time when its silver rind formed the canoes of our early British ancestors, such as have been found buried in the gravels of the banks of the Clyde. This etymology does not seem, however, to have suggested itself to Turner, since in his "Names of Herbes" (1548) he simply says:--" Betula--or, as some wryte it, betulla--is called in greeke, Semida; in englishe, a birch tree, or a birke tree; in duche, ein birck baum; in frenche, bouleau or beula. It groweth in woddes and forestes."
The genus Betula, to which the Birch belongs, includes some five-and-twenty species of shrubs and trees of medium size, confined to the northern hemisphere, and remarkable for their extension into Arctic latitudes. The Canoe, or Paper Birch (B. papyracea), of North America, is a variety of the White Birch, though stunted, and only occurring in an isolated manner within the Arctic Circle, reaching 70 deg N. lat., whilst another species (B. Bhojputtra) grows at an altitude of 9,000 feet in the Himalayas. Our own species, Betula alba, ascends to 2,500 feet in the Highlands, and is widely spread over Europe, Asia, and America, extending farther north than any other European tree, but only constituting an essential element of forest scenery as far south as 45 deg. Together with the Alders, of which there are some fourteen species, the Birches form the natural order Betulacea, catkin-bearing trees, with not more than five stamens to each flower, and with neither "perianth" or "cupule" (like those of Oaks, Hazels, Chestnut, or Beech) to enclose their small compressed fruits. The Birches differ from the Alders in the scales of the seed-bearing catkin being chafflike, and falling together with its winged fruits, whilst those of the Alders remain as a woody cone.
The White or Silver Birch is a short-lived tree, as a rule from forty to fifty feet high, though exceptionally growing to eighty feet, with a trunk seldom exceeding a foot in diameter, conspicuous from its flaking, silvery-white bark. This flaking is produced by the formation of alternate layers of larger and smaller cells in the "periderm," or outer bark, of which the larger are the more readily ruptured under the influence of variations in the degree of atmospheric moisture. Every careful observer will have noticed that this polished silver rind is interrupted at frequent intervals by transverse ridges of a darker color extending partly round the stem. These are the "lenticels," or breathing-pores of the bark, replacing the "stomata" of the young epidermis, and corresponding to the holes filled with powdery dried cells that extend through the cork of the Oak at right angles to its surface. As the stem or branch increases in diameter, these lenticels become stretched from mere spots into long lines.
It is when its slightly crooked stem stands alone on the slope of some river glen, brown with fallen leaves of autumn, and lit up by the varying hue of the dead fronds of bracken, with its round slender branches, of polished purple bronze, weeping in festoons eight or ten feet long, that the Birch is seen in all its beauty of outline. It is, however, when these bare boughs, or those of the smaller trees that dot the heathery wastes of Epping Forest or Bagshot Heath, begin to clothe themselves in April with their transparent foliage of fluttering brilliant leaflets, that the tree is, perhaps, at its perfection of grace and loveliness. When grouped together in numbers, a grove of young Birches in winter presents an almost smoke-like hazy effect of copper boughs and purple twigs springing round the slender silver stems; but in spring they lose all signs of somber melancholy, and seem to laugh as their leaves dance in the sunbeams which fall between them on to the dog-violets that strew the wood-side.
Linnaeus's species, Betula alba, includes several fairly distinct forms. Of these, B. verrucosa, Ehrh., is distinguished by its longer pendulous branches having white resinous tubercles on their bark, as also occasionally on the leaves, by its conical buds, by the reflexed sickle-shaped side-lobes of the scales of the fruiting catkins, and by the leaf. This is rhomboidally triangular, its long stalk passing abruptly into the blade, its veins projecting from the upper surface of the blade, and its point abruptly "acuminate," or tapering. B. glutinosa, Fries., on the other hand, is often a mere shrub; its buds are egg-shaped, the side lobes of the scales of its fruiting catkins are erect, and its leaf is rounded, or even heart-shaped, at the base, and has its veins projecting from the under surface, and its point acute, but not drawn out.
The northern form of this last, known as B. pubescens, Ehrh., differs mainly in the absence of tubercles and in the downiness of the leaves, peduncles, and twigs. In all the forms the branches succeed one another in what is termed a "cymose" manner, each axis being comparatively short; and the somewhat thick leaves on slender stalks, with broad "stipules" at the base and doubly-toothed margins, appear before the maturity of the catkins. This takes place in April and May, but even in February the pollen-bearing catkins may be seen forming on the twigs. These "male" catkins are borne at the ends of the shoots of the previous year, and are not protected with any winter bud-scales, whilst the "female," or fruiting catkins, terminate lateral dwarf shoots, which bear a few leaves, and are enclosed by budscales.
The pollen-bearing catkins are often nearly two inches long, each of their scales, or "bracts," having two lateral appendages, or "bracteoles," which protect three flowers, each with two forked stamens. The female catkins are shorter, and are at first erect. In them the two bracteoles cohere with the bract to form a three-lobed scale, which, as we have seen, falls off with the three fruits that are produced from its base, and the form of the side lobes of which distinguishes the sub-species. The little fruits are furnished with a broad membranous wing, which, together with their flattened form, aids in their dispersal by the wind. Their general outline is thus nearly circular, surmounted by two small styles, an indication of the original two chambers of the ovary, each with its one pendulous ovule, reduced in the fruit stage, by an abortion frequent among trees, to one chamber and one seed.
In early times not only did the Birch provide primitive man with his canoe, but it probably roofed his rude shanty, and furnished fiber for his cable, fishing-lines, or other cordage, in districts beyond the northern limit of the Linden. Probably, too, it was at no late period in the history of civilization that man took to tapping the white trunks in the spring for the sake of the copious flow of sugary sap, and to fermenting this sap into a wine or spirit, as is still done both in Sweden and in Leicestershire. It is a remarkable fact in sociology that there is hardly a country in the world that has not some alcoholic drink, and also some more innocuous infusion containing a vegetable alkaloid, similar to the theine, caffeine, and theobromine of tea, coffee, and cocoa. Besides a beer, prepared formerly from its young shoots, the Birch yields beverages of both these classes: the wine just mentioned, and a tea prepared from the leaves, chiefly by the Finlanders.
Shakespeare refers to this beautiful tree. In "Measure for Measure," he tells how fond fathers,
"Having bound up the threatening twigs of Birch,
Only to stick it in their children's sight
For terror, not to use, in time the rod
Becomes more mocked than feared."
Owing to the beautiful arrangement of the cells in the outer bark, to which reference has already been made, the Birch is constantly shedding its rind in strips that go right round the stem, and is thus, together with the similarly constituted Plane, one of the species best fitted to withstand the smoke of London.
This tree is, however, peculiarly liable to the disease known as "Witch Knots," or "Witches' Brooms," a confused mass of short twigs, like an old rook's nest, produced by a very minute gall-mite, Phytoptus, which attacks the young buds. It is desirable to burn all parts so affected, as the mites will otherwise be carried from tree to tree by wind or birds.
The Birch is remarkable for its power of holding its own, and spreading, amongst heather, where other species are commonly stifled unless protected. Thus, formerly it was not a common tree in Epping Forest, but, from this power and its enormous production of seeds, which are scattered far and wide by the wind, owing to the little wing attached to them, it is now spreading rapidly, springing up spontaneously wherever the soil is dry, if a clearing has been made by fire or felling. Allied species in North America have been noticed as having the same faculty--as being, in fact, well equipped for the battle for life
