Bark and leaves of Betula alba L., Betulaceae. Habit. Europe and Northern Asia, also America, north of Pennsylvania. Constit. 10-15% Betulin (betula camphor), betuloresinic acid, essential oil, saponins, betulol (sesquiterpene alcohol), apigenin dimethyl ether, betuloside, gaultherin, methyl salicylate, ascorbic acid. Ref: Kreitmair, Pharmazie 8, 534 (1953).