SALICACE^E 



155 



brown, orange-green, or nearly white, often roughened by horizontal bands of circular 

 wart-like excrescences, frequently marked below the branches by large rows of 

 lunate dark scars, becoming near the base of old trees nearly black, 2' thick, and 

 deeply divided into broad flat ridges broken on the surface into small appressed 

 plate-like scales. 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 

 northwesterly to the mouth of the Mackenzie River and the valley of the Yukon 

 River, Alaska, through the northern states to the mountains of Pennsylvania, north- 

 eastern Missouri and northwestern Nebraska, and through all the mountain regions 

 of the west, often ascending to elevations of 10,000 above the level of the sea, 

 to the sierras of central California, northern Arizona and New Mexico, the high 

 mountain ranges of Chihuahua and to Mt. San Pedro Martir in Lower California; in 

 the east common and generally distributed usually on moist sandy soil and gravelly 

 hillsides; bordering the midcontinental prairie region with a wide belt, and growing 

 with its greatest vigor and to its largest size on the western margin of the Atlantic 

 forest north of the 49th degree; farther to the northwest forming with the Birch 

 and the Spruce the forests of high ridges; in the west and southwest on the high 

 slopes of mountains and along the'banks of streams; 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; now widely spread over vast areas of the slopes 

 of the Rocky Mountains swept by fire of their former covering of coniferous trees. 



2. Populus grandidentata, Michx. Poplar. 



Leaves broadly ovate, short-pointed and coarsely and irregularly crenate, with 

 stout incurved callous teeth except at the broad abruptly wedge-shaped truncate or 

 rounded base, thin and firm in texture, dark green above, paler on the lower surface, 



3'-4' long, 2'-3' broad, with prominent yellow midribs, conspicuously forked veins, 

 and reticulate veinlets, their petioles slender, laterally compressed, \%-l\' long. 

 Flowers: aments l^'-2' long, the pistillate becoming 4'-5' long at maturity, 

 their scales pale and scarious below, divided above into 5 or 6 small irregular 

 acute lobes covered with soft pale hairs; disk shallow, oblique, the staminate entire, 



