Part 30 (2/2)

GENUS =83. BeTULA.=

Trees or shrubs with simple, alternate, mostly straight-veined, thin, usually serrate leaves. Flowers in catkins, opening in early spring, in most cases before the leaves. Fruit a leafy-scaled catkin or cone, hanging on till autumn. Twigs usually slender, the bark peeling off in thin, tough layers, and having peculiar horizontal marks. Many species have aromatic leaves and twigs.

* Trunks with chalky white bark. (=A.=)

=A.= Native. (=B.=)

=B.= Small tree with leafstalks about 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 s.h.a.ggy on the main trunk; growing in or near the water 6.

[Ill.u.s.tration: B. populiflia.]

1. =Betula populiflia=, 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 s.h.i.+ning, 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 s.p.a.ces below the branches; recent shoots brown, closely covered with round dots.

[Ill.u.s.tration: B. papyrifera.]

2. =Betula papyrifera=, 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.

[Ill.u.s.tration: B. alba.]

3. =Betula alba=, L. (EUROPEAN WHITE BIRCH.) Leaves ovate, acute, somewhat deltoid, unequally serrate, often deeply cut, nearly smooth; in var. _p.u.b.escens_ 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 _p.u.b.escens_ (hairy-leaved).

[Ill.u.s.tration: B. lenta.]

4. =Betula lenta=, 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 s.h.i.+ning green above, smooth beneath, except the veins, which are hairy. Fruit 1 to 1 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.

[Ill.u.s.tration: B. lutea.]

5. =Betula lutea=, 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 coa.r.s.ely 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.

[Ill.u.s.tration: B. ngra.]

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