Populus in the extreme north often forms great forests, and is common on the alluvial bottom-lands of streams and on high mountain slopes, ranging from the Arctic Circle to northern Mexico and Lower California and from the Atlantic to the Pacific in the New World, and to northern Africa, the southern slopes of the Himalayas, central China, and Japan in the Old World. Of the thirty-four species now generally recognized fifteen are found in North America. The wood of many of the American species is employed in large quantities for paper-making, and several species furnish wood used in construction and in the manufacture of small articles of wooden ware. The bark contains tannic acid and is used in tanning leather and occasionally as a tonic, and the fragrant balsam contained in the buds of some species is occasionally used in medicine. The rapidity of their growth, their hardiness and the ease with which they can be propagated by cuttings, make many of the species useful as ornamental trees or in wind-breaks, although planted trees often suffer severely from the attacks of insects boring into the trunks and branches. Of the exotic species, the Abele, or White Poplar, Populus alba L., of Europe and western Asia, and its fastigiate form, and the so-called Lombardy Poplar, a tree of pyramidal habit and a form of the European and Asiatic Populus nigra L., and one of its hybrids, have been largely planted in the United States.
Populus, of obscure derivation, is the classical name of the Poplar.
CONSPECTUS OF THE NORTH AMERICAN SPECIES.
Stigmas 2, 2-lobed, their lobes filiform; leaf stalks elongated, laterally compressed; buds slightly resinous. Leaves finely serrate; winter-buds glabrous.1. [P. tremuloides] (A, B, F, G). Leaves coarsely serrate; winter-buds tomentose or pubescent.2. [P. grandidentata.] Stigmas 2—4, 2-lobed and dilated, their lobes variously divided; buds resinous. Leaf-stalks round. Leaves tomentose below early in the season, broadly ovate, acute or rounded at apex.3. [P. heterophylla] (A, C). Leaves glabrous or pilose below. Leaves dark green above, pale, rarely pilose below. Ovary and capsule glabrous.4. [P. tacamahacca] (A, B, F). Ovary and capsule tomentose or pubescent.5. [P. trichocarpa] (B, F). Leaves light green on both surfaces, glabrous. Leaves lanceolate to ovate-lanceolate.6. [P. angustifolia] (F). Leaves rhombic-lanceolate to ovate.7. [P. acuminata] (F). Leaf-stalks laterally compressed. Leaves without glands at apex of the petiole, coarsely serrate, thick. Pedicels shorter than the fruit. Disk cup-shaped. Branchlets stout; capsule ⅓′—½′ long.8. [P. Fremontii] (G, H). Branchlets slender; capsule not more than ¼′ long.9. [P. arizonica] (F, H). Disk minute. Branchlets glabrous; leaves broad-ovate to deltoid, long-pointed and acuminate at apex.10. [P. texana] (C). Branchlets pubescent; leaves broad-ovate, abruptly short-pointed or acute at apex.11. [P. McDougallii] (G, H). Pedicels 2 or 3 times longer than the fruit; leaves broadly deltoid, abruptly short-pointed.12. [P. Wislizenii] (E, F). Leaves furnished with glands at apex of the petiole. Branchlets stout; leaves thick. Winter-buds puberulous; leaves coarsely serrate; branchlets light yellow.13. [P. Sargentii] (F). Winter-buds glabrous; leaves less coarsely serrate; branchlets gray or reddish brown.14. [P. balsamifera] (A, C). Branchlets slender; leaves thin, ovate, cuneate or rounded at base, finely serrate.15. [P. Palmeri] (E).
1. [Populus tremuloides] Michx. Aspen. Quaking Asp.
Leaves ovate to broad-ovate or rarely reniform (var. reniformis Tidestrom) abruptly short-pointed or acuminate at apex rounded or rarely cuneate at the wide base, closely crenately serrate with glandular teeth, thin, green and lustrous above, dull green or rarely pale below, up to 4½′ long and broad with a prominent midrib, slender primary veins and conspicuous reticulate veinlets; petioles slender, compressed laterally, 1½′—3′ long. Flowers: aments 1½′—2½′ long, the pistillate becoming 4′ in length at maturity; scales deeply divided into 3—5 linear acute lobes fringed with long soft gray hairs; disk oblique, the staminate entire, the pistillate slightly crenate; stamens 6—12; ovary conic, with a short thick style and erect stigmas thickened and club-shaped below and divided into linear diverging lobes. Fruit maturing in May and June, oblong-conic, light green, thin-walled, nearly ¼′ long; seeds obovoid, light brown, about 1/32′ in length.
A tree, 20°—40° high, with a trunk 18′—20′ in diameter, slender remote and often contorted branches somewhat pendulous toward the ends, forming a narrow symmetrical round-topped head, and slender branchlets covered with scattered oblong orange-colored lenticels, bright red-brown and very lustrous during their first season, gradually turning light gray tinged with red, ultimately dark gray, and much roughened for two or three years by the elevated leaf-scars. Winter-buds slightly resinous, conic, acute, often incurved, about ¼′ long, narrower than the more obtuse flower-buds, with 6 or 7 lustrous glabrous red-brown scales scarious on the margins. Bark thin, pale yellow-brown or orange-green, often roughened by horizontal bands of circular wart-like excrescences, frequently marked below the branches by large rows of lunate dark scars. Wood light brown, with nearly white sapwood of 25—30 layers of annual growth.
Distribution. Southern Labrador to the southern shores of Hudson’s Bay and northwesterly to the mouth of the Mackenzie River, through the northern states to the mountains of Pennsylvania, northern Ohio, Indiana and Illinois, eastern and central Iowa and northeastern Missouri; common and generally distributed usually on moist sandy soil and gravelly hillsides; most valuable in the power of its seeds to germinate quickly in soil made infertile by fire and of its seedlings to grow rapidly in exposed situations; westward passing into the var. aurea Daniels, with thicker rhombic to semiorbicular or broad-ovate generally smaller leaves, usually pale on the lower surface, rounded or acute and minutely short-pointed at apex, rounded or cuneate at base, often entire with slightly thickened margins, or occasionally coarsely crenately serrate, with inconspicuous reticulate veinlets, turning bright golden yellow in the autumn before falling.
A tree occasionally 100° high with a trunk up to 3° in diameter, with pale often white bark, becoming near the base of old stems 2′ thick, nearly black, and deeply divided into broad flat ridges broken on the surface into small appressed plate-like scales.