156 TREES OF NORTH 



the pistillate slightly crenate; stamens 6-12, with short slender filaments and light 

 red anthers; ovary oblong-conical, bright green, puberulous, with a short style and 

 spreading stigmas divided nearly to the base into elongated filiform lobes. Fruit 

 ripening as the leaves unfold, often more or less curved above the middle, light 

 green and puberulous, thin-walled, 2-valved, about \' long, and raised on a slender 

 pubescent stalk; seeds minute, dark brown. 



A tree, often 60-70 high, with a trunk occasionally 2 in diameter, and slender 

 rather rigid branches forming a narrow round-topped head, and stout branchlets 

 marked with scattered oblong orange-colored lenticels, coated at first like the un- 

 folding leaves, their petioles and stipules with thick short hoary deciduous tomentum, 

 becoming during their first year dark red-brown or dark orange-colored and glabrous 

 or lustrous, or covered with a delicate gray pubescence, and in their second year 

 dark gray sometimes slightly tinged with green and much roughened by the elevated 

 3-lobed leaf-scars; generally smaller and usually not more than 30-40 tall. Win- 

 ter-buds terete, broadly ovate, acute, with light bright chestnut-brown scales, pu- 

 berulous during the winter especially on their thin scarious margins, about \' long 

 and not more than half the size of the flower-buds. Bark thin, smooth, light gray 

 tinged with green, becoming near the base of old trunks f '-!' thick, dark brown 

 tinged with red, irregularly fissured and divided into broad flat ridges roughened on 

 the surface by small thick closely appressed scales. Wood light brown, with thin 

 nearly white sapwood of 20-30 layers of annual growth. 



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 northern Delaware, southern 

 Indiana and Illinois, northeastern and central Iowa, and along the Alleghany Moun- 

 tains to North Carolina, and westward to central Kentucky and Tennessee. 



2. Stigmas 2-4 ; capsules 2-4-valved buds very resinous. 

 * Leaf -stalks round. 



3. Populus heterophylla, L. Swamp Cottonwood. Black Cottonwood. 



Leaves broadly ovate, gradually narrowed and acute, short-pointed or rounded at 

 the apex, slightly cordate or truncate or rounded at the broad base, usually fur- 

 nished with a narrow deep sinus, finely or coarsely crenate, with small incurved 

 glandular teeth, covered as they unfold with thick hoary tomentum soon deciduous 

 from the upper surface, becoming thin and firm in texture, dark deep green above, 

 pale and glabrous below, with stout yellow midribs, forked veins and conspicuous 

 reticulate veinlets, 4'-7' long, 3'-6' broad, with slender terete tomentose or nearly 

 glabrous petioles 2^'-3^' long. Flowers: staminate aments broad, densely flowered, 

 1' long, erect when the flowers first open, becoming pendulous and 2'-2|' long, their 

 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, 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 



