122 



TREES OF NORTH AMERICA 



thickened margins, or occasionally coarsely crenately serrate, with inconspicuous reticulate 

 veinlets, turning bright golden yellow in the autumn before falling. 



A tree occasionally 100 high with a trunk up to 3 in diameter, with pale often white 

 bark, becoming near the base of old stems 2' thick, nearly black, and deeply divided into 

 broad flat ridges broken on the surface into small appressed plate-like scales. 



Distribution. Valley of the Yukon River to Saskatchewan, and southward through the 

 mountain ranges of the Rocky Mountain region to southern New Mexico, the San Francisco 

 Mountains of Arizona, and westward to the valley of the Skeena River, British Columbia, 

 western Washington and Oregon, the western slopes of the Sierra Nevada and the high 

 mountains of southern California, and eastward to North and South Dakota and western 

 Nebraska; on the mountains of Chihuahua, and on the Sierra de Laguna, Lower California. 



Populus tremuloides var. vancouveriana Sarg. 

 Populus vancouveriana Trel. 



Leaves broadly ovate to semiorbicular, abruptly short-pointed or rounded at apex, 

 rounded or slightly cordate at the broad base, coarsely crenately serrate and sometimes 

 obscurely crispate on the margins, when they unfold covered below and on the petioles with 



Fig. 116 



a thick coat of long matted pale hairs, and slightly villose, glabrous or nearly glabrous above, 

 soon glabrous, and at maturity thick dark green, lustrous and scabrate on the upper surface, 

 paler on the lower surface, 3'-4^' long and broad, with a prominent midrib and primary 

 veins; petioles slender, compressed, becoming glabrous, 2'-3' in length. Flowers: stami- 

 nate aments slightly villose; pedicels pubescent; disk of the flower puberulous toward the 

 base; flowers as in the species; pistillate aments 2'-2' long, becoming 3-3^' in length at 

 maturity; the rachis, pedicels and slightly lobed disk of the flower densely villose-pubes- 

 cent; ovary conic, pubescent, with a short style and stigma divided into narrow divergent 

 lobes. Fruit on pedicel not more than ^V in length, oblong-conic, pubescent or glabrous, 

 long. 



A tree 30-36 high, with a trunk 12'-16' in diameter, stout spreading branches forming 

 a round-topped head, stout, reddish brown pubescent or puberulous branchlets often be- 

 coming glabrous during their first summer. Winter-buds acute, tomentose, pubescent 

 or glabrous. 



