FLOWERS.—April-May, with the leaves; dioecious; borne in slender, nearly glabrous catkins 1-2 inches long; calyx 0; corolla 0; scales ovate-lanceolate, slightly hairy; ovary ovoid-conical, very short-stalked, with stigmas longer than the style. Staminate trees apparently do not occur in the United States.

FRUIT.—May-June; 1-celled, narrow-ovoid, sessile capsule, about 3/16 inch long, containing many minute seeds which are furnished with long, silky, white hairs.

WINTER-BUDS.—Terminal bud absent; lateral buds narrow-conical, sharp-pointed, somewhat flattened, brownish, 1/8-1/4 inch long.

BARK.—Twigs glabrous, olive-green; thick and gray on old trunks, rather smooth, or irregularly fissured into shallow, firm ridges.

WOOD.—Light, soft, weak, close-grained, light brown, with thick, whitish sapwood.

NOTES.—A native of Europe and Asia. Often grown in cemeteries. Easily propagated by cuttings. Rapid of growth in rich, damp soil. Sometimes winter-killed because the wood is not ripened.

SUMMER KEY TO THE SPECIES OF POPULUS

a.Leaf-petioles essentially terete.
b.Petioles and lower sides of leaves pubescent; leaves heart-shaped.P. candicans, p. [55].
bb.Petioles and lower sides of leaves glabrous; leaves ovate-lanceolate.P. balsamifera, p. [53].
aa.Leaf-petioles strongly flattened.
b.Petioles and lower sides of leaves tomentose; twigspubescent.P. alba, p. [47].
bb.Petioles and lower sides of leaves glabrous; twigs glabrous.
c.Leaves distinctly deltoid in shape.
d.Leaves broader than they are long, abruptly acuminateat the apex; marginal teeth not conspicuously incurved;branches erect and more or less appressed tothe main stem, forming a narrow, spire-like crown.P. nigra italica, p. [59].
dd.Leaves longer than they are broad, more or less taper-pointedat the apex; marginal teeth rather conspicuouslyincurved; branches spreading, forming a broadcrown.P. deltoides, p. [57].
cc.Leaves ovate to nearly orbicular in shape.
d.Margin of leaves coarsely sinuate-toothed; leaves 3-5inches long.P. grandidentata, p. [51].
dd.Margin of leaves finely serrate; leaves less than 3inches long.P. tremuloides, p. [49].