Distribution. Rich moist sandy soil near the borders of swamps and streams; Nova Scotia, through New Brunswick, southern Quebec and Ontario to northern Minnesota, southward through the northern states to Pennsylvania, northern Ohio, and eastern (Muscatine County) and central Iowa, and westward to central Kentucky and Tennessee; passing into the var. _meridionalis_ Tidestrom with broad-ovate acuminate leaves with more numerous teeth, often 4′—5′ long and 3′ wide; the common form in Maryland, northern Delaware, the piedmont region of Virginia and North Carolina, southern Ohio, and southern Indiana and Illinois; rare northward to northern New England.
3. Populus heterophylla L. Swamp Cottonwood. Black Cottonwood.
Leaves broadly ovate, gradually narrowed and acute, short-pointed or rounded at apex, slightly cordate or truncate or rounded at the wide base, usually furnished with a narrow deep sinus, finely or coarsely crenately serrate with incurved glandular teeth, covered as they unfold with thick hoary deciduous tomentum, becoming thin and firm in texture, dark deep green above, pale and glabrous below, with a stout yellow midrib, forked veins and conspicuous reticulate veinlets, 4′—7′ long, 3′—6′ wide; petioles slender terete tomentose or nearly glabrous 2½′—3½′ in length. Flowers: staminate aments broad, densely flowered, 1′ long, erect when the flowers first open, becoming pendulous and 2′—2½′ long; scales narrowly oblong-obovate, brown, scarious and glabrous below, divided into numerous elongated filiform light red-brown lobes; disk oblique, slightly concave; stamens 12—20, with slender filaments about as long as the large dark red anthers; pistillate aments slender, pendulous, few-flowered, 1′—2′ long, becoming erect and 4′—6′ long before maturing, their scales concave and infolding the flowers, linear-obovate, brown and scarious, laterally lobed, fimbriate above the middle, caducous; disk thin, irregularly divided in numerous triangular acute teeth, long-stalked; ovary ovoid, terete or obtusely 3-angled, with a short stout elongated style and 2 or 3 much-thickened dilated 2 or 3-lobed stigmas. Fruit on elongated pedicels, ripening when the leaves are about one third grown, ovoid, acute, dark red-brown, rather thick-walled, 2 or 3-valved, about ½′ long; seeds obovoid, minute, dark red-brown.