BETULA, or BIRCH-TREE, in botany, a genus of the monœcia tetrandria class. The calix of the male flower has but one trifid leaf, and incloses three flowers; the corolla consists likewise of one leaf cut into four segments. The calix of the female is trifid, and incloses two flowers; and the seed is membranous, and alated on each side. The species are five, viz. the alba or birch-tree, a native of Britain; the nigra, and lenta, both natives of America; the nana, a native of Lapland, Russia, and Sweden; and the alnus, likewise a native of Lapland. The bark of the alba, or common birch-tree, is a highly inflammable substance; but its medical virtues are little known. Upon boring the trunk in the beginning of spring, a sweetish juice issues forth in great quantities; one branch will bleed an English gallon or more in a day. This juice is chiefly recommended in scorbutic disorders, and other
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foulnesses of the blood: Its most sensible effect is to promote the urinary discharge.