Distribution. Low often inundated river-bottom lands and swamp borders; Labrador to latitude 65° north in the valley of the Mackenzie River, and to the Alaskan coast, south to northern New England and New York, central Michigan, Minnesota (except in southern and southwestern counties), Turtle Mountains, Rolette County, North Dakota, the Black Hills of South Dakota, northwestern Nebraska (basin of Hat Creek), and in Colorado; the characteristic tree on the streams of the prairie region of British America, attaining its greatest size on the islands and banks of the Peace, Athabasca, and other tributaries of the Mackenzie; common in all the region near the northern boundary of the United States from Maine to the western limits of the Atlantic forests; the largest of the sub-Arctic American trees, and in the far north the most conspicuous feature of vegetation; passing into the variety _Michauxii_ Farwell, with more cordate leaves, slightly pilose on the under side of the midrib and veins; common from Aroostook County, Maine, to the Province of Quebec, Newfoundland, and the shores of Hudson Bay. Often planted at the north for shelter or ornament. _Populus candicans_ Ait., the Balm of Gilead of which only the pistillate tree is known, has often been considered a variety of the North American Balsam Poplar. This tree has been long cultivated in the northeastern part of the country and has sometimes escaped from cultivation and formed groves of considerable extent, as on the banks of Cullasagee Creek on the western slope of the Blue Ridge in Macon County, North Carolina. The fact that only one sex is known suggests hybrid origin but of obscure and possibly partly of foreign origin. 5. Populus trichocarpa Hook. Black Cottonwood. Balsam Cottonwood. [Illustration: Fig. 120] Leaves broad-ovate, acute or acuminate at apex, rounded or abruptly cuneate at base, finely crenately serrate, glabrous, dark green above, pale and rusty or silvery white and conspicuously reticulate-venulose below, 3′—4′ long, 2′—2½′ wide; petioles slender, pubescent, puberulous, pilose or rarely glabrous, 1½′—2′ in length. Flowers: aments stalked, villose-pubescent, the staminate densely flowered, 1½′—2′ long, ⅓′ thick, the pistillate loosely flowered, 2½′—3′ long, becoming 4′—5′ long before the fruit ripens; scales dilated at the apex, irregularly cut into numerous filiform lobes, glabrous or slightly puberulous on the outer surface; disk of the staminate flower broad, slightly oblique; stamens 40—60, with slender elongated filaments longer than the large light purple anthers; disk of the pistillate flower deep cup-shaped, with irregularly crenate or nearly entire revolute margins; ovary subglobose, coated with thick hoary tomentum, with 3 nearly sessile broadly dilated deeply lobed stigmas. Fruit subglobose, nearly sessile, pubescent, thick-walled, 3-valved; seeds obovoid, apiculate at the gradually narrowed apex, light brown, puberulous toward the ends, 1/12′ long.