124 



TREES OF NORTH AMERICA 



southward through the northern states to Pennsylvania, northern Ohio, and eastern (Mus- 

 catine County) and central Iowa, and westward to central Kentucky and Tennessee; 

 passing into the var. meridwnalis 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 south- 

 ern 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 2'-3| in length. Flowers: staminate aments broad, densely flowered, 

 1' long, erect when the flowers first open, becoming pendulous and 2'-2f long; scales nar- 

 rowly oblong-obovate, brown, scarious and glabrous below, divided into numerous elon- 



Fig. 118 



gated 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, l'-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 \' long; seeds obovoid, minute, dark 

 red-brown. 



A tree, 80-90 high, with a tall trunk 2-3 in diameter, short rather slender branches 

 forming a comparatively narrow round-topped head, and stout branchlets, marked by 

 small elongated pale lenticels, coated at first with hoary caducous tomentum, becoming 

 dark brown and rather lustrous or ashy gray, or rarely pale orange color and glabrous or 

 slightly puberulous, or covered with a glaucous bloom in their first winter, growing darker 

 in their second year and much roughened by the large thickened leaf-scars; usually much 

 smaller and at the north rarely more than 40 tall. Winter-buds slightly resinous, broadly 

 ovoid, acute, with bright red-brown scales, about \' long and about one half the size of the 



