2. Bétula papyrífera, Marsh. (Paper or Canoe Birch.) Leaves 2 to 4 in. long, ovate, taper-pointed, heart-shaped, abrupt or sometimes wedge-shaped at the base, sharply and doubly serrate, smooth and green above, roughly reticulated, glandular-dotted and slightly hairy beneath; footstalk not over 1/3 the length of the blade. Fruit long-stalked and drooping. A large tree, 60 to 75 ft. high, with white bark splitting freely into very thin, tough layers. A variety, 5 to 10 ft. high (var. minor), occurs only in the White Mountains. Young shoots reddish or purplish olive-green deepening to a dark copper bronze. New England and westward, also cultivated.
B. álba.
3. Bétula álba, L. (European White Birch.) Leaves ovate, acute, somewhat deltoid, unequally serrate, often deeply cut, nearly smooth; in var. pubescens covered with white hairs. Fruit brown, cylindric, drooping. A tree, 30 to 60 ft. high, with a chalky-white bark; from Europe, extensively cultivated in this country, under many names, which indicate the character of growth or foliage; among them may be mentioned pendula (weeping), laciniata (cut-leaved), fastigiata (pyramidal), atropurpurea (purple-leaved), and pubescens (hairy-leaved).
B. lénta.
4. Bétula lénta, L. (Sweet, Black or Cherry Birch.) Leaves and bark very sweet, aromatic. Leaves ovate or ovate-oblong, with more or less heart-shaped base, very acute apex, and doubly and finely serrate margin, bright shining green above, smooth beneath, except the veins, which are hairy. Fruit 1 to 1¼ in. long, cylindric, with spreading lobes to the scales. A rather large tree, 50 to 70 ft. high, with bark of trunk and twigs in appearance much like that of the garden Cherry, and not splitting into as thin layers as most of the Birches. Wood rose-colored, fine-grained. Moist woods, rather common throughout; also cultivated.
B. lùtea.
5. Bétula lùtea, Michx. f. (Yellow or Gray Birch.) A species so like the preceding (Betula lenta) as to be best described by stating the differences. Leaves and bark are much less aromatic. Leaves 3 to 5 in. long, not so often nor so plainly heart-shaped at base, usually narrowed; less bright green above, and more downy beneath; more coarsely serrate. Fruit not so long, and more ovate, with much larger and thinner scales, the lobes hardly spreading. A large tree, 50 to 90 ft. high, with yellowish or silvery-gray bark peeling off into very thin, filmy layers from the trunk. Wood whiter, and not so useful. Rich, moist woodlands, especially northward; also cultivated.