* Trunks with chalky white bark. (=A.=) =A.= Native. (=B.=) =B.= Small tree with leafstalks about ½ as long as the blades 1. =B.= Large tree; leafstalks about 1/3 as long as the blades 2. =A.= Cultivated; from Europe; many varieties 3. * Bark not chalky white, usually dark. (=C.=) =C.= Leaves and bark very aromatic. (=D.=) =D.= Bark of trunk yellowish and splitting into filmy layers 5. =D.= Bark not splitting into filmy layers 4. =C.= Leaves not very aromatic; bark brownish and loose and shaggy on the main trunk; growing in or near the water 6. [Illustration: B. populifòlia.] 1. =Bétula populifòlia=, Ait. (AMERICAN WHITE OR GRAY BIRCH.) Leaves triangular, very taper-pointed, and usually truncate or nearly so at the broad base, irregularly twice-serrate; both sides smooth and shining, when young glutinous with resinous glands; leafstalks half as long as the blades and slender, so as to make the leaves tremulous, like those of the Aspen. Fruit brown, cylindrical, more or less pendulous on slender peduncles. A small (15 to 30 ft. high), slender tree with an ascending rather than an erect trunk. Bark chalky or grayish white, with triangular dusky spaces below the branches; recent shoots brown, closely covered with round dots. [Illustration: B. papyrífera.] 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. [Illustration: 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). [Illustration: B. lénta.]