SALICACE^E 121 



1. Populus tremuloides Michx. Aspen. Quaking Asp. 



Leaves ovate to broad-ovate or rarely reniform (var. reniformis Tidestrom) abruptly short- 

 pointed or acuminate at apex rounded or rarely cuneate at the wide base, closely crenately 

 serrate with glandular teeth, thin, green and lustrous above, dull green or rarely pale below, 

 up to 4|' long and broad with a prominent midrib, slender primary veins and conspicuous 

 reticulate veinlets; petioles slender, compressed laterally, l|'-3' long. Flowers: aments 

 l|'-2f long, the pistillate becoming 4' in length at maturity; scales deeply divided into 

 3-5 linear acute lobes fringed with long soft gray hairs; disk oblique, the staminate entire, 

 the pistillate slightly crenate; stamens 6-12; ovary conic, with a short thick style and erect 

 stigmas thickened and club-shaped below and divided into linear diverging lobes. Fruit 

 maturing in May and June, oblong-conic, light green, thin-walled, nearly ' long; seeds 

 obovoid, light brown, about jz' in length. 



A tree, 20-40 high, with a trunk 18'-20' in diameter, slender remote and often con- 

 torted branches somewhat pendulous toward the ends, forming a narrow symmetrical 



Fig. 115 



round-topped head, and slender branchlets covered with scattered oblong orange-colored 

 lenticels, bright red-brown and very lustrous during their first season, gradually turning 

 light gray tinged with red, ultimately dark gray, and much roughened for two or three 

 years by the elevated leaf-scars. Winter-buds slightly resinous, conic, acute, often in- 

 curved, about \' long, narrower than the more obtuse flower-buds, with 6 or 7 lustrous 

 glabrous red-brown scales scarious on the margins. Bark thin, pale yellow-brown or 

 orange-green, often roughened by horizontal bands of circular wart-like excrescences, fre- 

 quently marked below the branches by large rows of lunate dark scars. Wood light 

 brown, with nearly white sapwood of 25-30 layers of annual growth. 



Distribution. Southern Labrador to the southern shores of Hudson's Bay and north- 

 westerly to the mouth of the Mackenzie River, through the northern states to the moun- 

 tains of Pennsylvania, northern Ohio, Indiana and Illinois, eastern and central Iowa 

 and northeastern Missouri; common and generally distributed usually on moist sandy 

 soil and gravelly hillsides; most valuable in the power of its seeds to germinate quickly in 

 soil made infertile by fire and of its seedlings to grow rapidly in exposed situations; west- 

 ward passing into the var. aurea Daniels, with thicker rhombic to semiorbicular or broad- 

 ovate generally smaller leaves, usually pale on the lower surface, rounded or acute and 

 minutely short-pointed at apex, rounded or cuneate at base, often entire with slightly 



