126 TREES OF NORTH AMERICA 



more or less contorted near the ends, forming a comparatively narrow open head, and 

 glabrous or occasionally pubescent branchlets marked by oblong bright orange-colored 

 lenticels, much roughened by the thickened leaf-scars, at first red-brown and glabrous or 

 pubescent, becoming bright and lustrous in their first winter, dark orange-colored in their 

 second year, and finally gray tinged with yellow-green; usually much smaller toward the 

 southern limits of its range. Winter-buds saturated with a yellow balsamic sticky exuda- 

 tion, ovoid, terete, long-pointed; terminal I' long, f broad; axillary about f long, iV 

 broad, with 5 oblong pointed concave closely imbricated thick chestnut-brown lustrous 

 scales. Bark light brown tinged with red, smooth or roughened by dark excrescences, be- 

 coming on old trunks f'-l' thick, gray tinged with red, and divided into broad rounded 

 ridges covered by small closely appressed scales. Wood light brown, with thick nearly 

 white sap wood. 



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, 

 lias 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. 



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'-2f wide; petioles slender, pubes- 

 cent, puberulous, pilose or rarely glabrous, l'-2' in length. Flowers: aments stalked, 

 villose-pubescent, the staminate densely flowered, l'-2' long, $' thick, the pistillate loosely 

 flowered, 2^'-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 sub- 

 globose, 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, iV long. 



A tree, 30-100 high, with a trunk l-3 in diameter, erect branches forming an open 

 head, and slender branchlets terete or slightly angled while young, marked by many orange- 

 colored lenticels, glabrous or when they first appear coated with deciduous rufous or pale 

 pubescence, reddish brown during their first year, gradually becoming dark gray, and 

 roughened by the greatly enlarged and thickened elevated leaf-scars. Winter-buds resin- 



