BIRCH. Betula, a genus of plants of the natural order Betulacew. The order contains two important genera, birch and alder, the plants of which are all trees or shrubs, natives of tem perate and cold regions.
The genus Betula is distinguished by ten to twelve stamens, and winged achenia. The com mon birch (Betula alba) has small, triangu lar, doubly serrated leaves. It is a very beatiti ful forest tree, abounding in the north of Europe and of Asia. often forming large groves by itself. In the south of Europe it is found only upon mountains of considerable elevation. It is a tree of rapid growth. In favorable situations it at tains the height of 60 or even 70 feet, with diameter of or 2 feet. In the northern, or ut most alpine limits of vegetation, it only appears as a stunted bush. The bark is smooth and si1• very white, and its outermost layers are thrown off as the tree advances in age. The smaller brandies are very slender and flexible, and in a particularly graceful variety called the weeping 1 birch (Betula pendula of some botanists) they are still more slender, elongated, and pendulous.
The bark and leaves of the birch are, in sonic northern countries, used medicinally in eases of fever and eruptions. The bark is also used for yellow dye. It is in some countries made into shoes, hats, drinking-cups, etc. In many parts of the north of Europe it is used instead of slates or shingles by the peasantry; and in Russia—the outer or white layers being subjected to distilla tion—there is obtained a reddish empyreumatic oil called birch oil: it yields also the birch tar, or degutt, which is employed in the preparation of Russia leather. The wood is in universal use in northern countries for a great variety of pur poses. It is white, firm, and tough, and is em ployed by wheelwrights, coopers, turners, etc. It is much employe.1 fcr smoking hams, herrings, etc., because of the flavor which it imparts. Much of it is made into charcoal for forges. In the highlands of Scotland, and in many other countries, the sap is used, either in a fresh or in a fermented state, as a beverage. The white birch of North America (Betula populifolia) very nearly resembles the common birch, but is of much less value. It is found as far south as Pennsylvania. The wood is scarcely used. The black birch, or river birch, of North America (Betula nigra), also sometimes called red birch, is very similar to the common birch, and pro duces very hard and valuable timber. It attains the height of 70 feet. The bark is of a dark
color, the epidermis in the younger trees red dish. The name black birch is also given to a species that is found in the more northern parts of North America and is sometimes called the sweet birch, or cherry birch (Betula lenta); this also is a tree 70 feet or more in heignt, of which the timber is fine-grained. and valuable for making furniture and for other purposes. The bark of this species yields an essential oil identical with oil of wintergreen. Its leaves, when bruised, diffuse a sweet odor. and, when carefully dried, make an agreeable tea. The yellow birch of North America (Betula !idea) is a tree 70 to SO feet high, destitute of branches for 30 to 40 feet. and remarkable for its large leaves, which are 3 to 5 inches long, as well as for the brilliant golden yellow color of the epi dermis. It is found in Nova Scotia. New Bruns wick. Maine, etc. Its timber is used in ship building. The young saplings of all these Ameri can species are much employed for making hoops for casks. The paper birch (Betula papyrifera) is found in the northern parts of North America. It attains the height of 70 feet. The bark of the young trees is of a brilliant whiteness. and capa ble of division into very thin sheets, which have been used as a substitute for paper. It is used by the Indians for canoes, boxes, buckets, baskets, etc. The wood is used for the same purposes as that of the common birch. The mountainous districts of India produce several species of Betula. Thin, delicate strips of the bark of the Betula utilis are used for lining the tubes of hookahs. They were formerly used as writing paper. Betula alnoides. a native of the moun tains of Nepal, is a tree 50 to 60 feet high. cov ered with branches from the base, and of an oval form. Its wool is strong and durable. The dwarf birch (Betala nana) is a mere bushy shrub, seldom more than 2 or 3 feet high, and generally much less. It has orbicular crenate leaves. It is a native of the northern regions of the globe, and is found in some parts of the highlands of Scotland. It is interesting because of its uses to the Laplanders and other inhabi tants of very northern regions, tb whom it sup plies their chief fuel and the material with which they stuff their beds. Its seeds are food for the ptarmigan, which is useful to the Lap landers. For illus, see plate BRAKE AND BIRCH.
Fossil forms of birch are found in the Creta ceous rocks of Greenland and in the Tertiaries of Europe and North America.