164 TREES OF NORTH AMERICA 



into filiform lobes ; disk of the staminate flower broad, oblique, slightly thickened 

 and revolute on the margins ; stamens 60 or more, with short filaments and large 

 dark red anthers; disk of the pistillate flower broad cup-shaped; ovary subglobose, 

 with 3 or 4 nearly sessile dilated or laciniately lobed stigmas. Fruit oblong-ovate, 

 rather abruptly contracted and acute at the apex, slightly pitted, thin-walled, \'-\' 

 long, dark green, 3 or 4-valved, its stem %'-%' long ; seeds oblong-obovate, rounded 

 at the apex, light brown, about ^' long. 



A tree, sometimes 100 high, with a trunk occasionally 7-8 in diameter, divided 

 often 20-30 above the ground into several massive limbs spreading gradually 

 and becoming pendulous toward the ends, and forming a graceful rather open head 

 frequently 100 across, or on young trees nearly erect above and spreading below 

 almost at right angles with the stem, and forming a symmetrical pyramidal head, 

 and stout branchlets marked with long pale lenticels, terete or, especially on vigor- 

 ous trees, becoming angled in their second year, with thin more or less prominent 

 wings extending downward from the two sides and the bases of the large 3-lobed leaf- 

 scars. Winter-buds very resinous, ovate, acute, the lateral much flattened, ^' long, 

 with 6 or 7 light chestnut-brown lustrous scales. Bark thin, smooth, light yellow 

 tinged with green on young stems and branches, becoming on old trunks l^'-2' thick, 

 ashy gray, and deeply divided into broad rounded ridges broken into closely ap- 

 pressed scales. Wood dark brown, with thick nearly white sapwood, warping badly 

 in drying and difficult to season. 



Distribution. Banks of streams, often forming extensive open groves; Province 

 of Quebec and the shores of Lake Champlain, through western New England and 

 New York, Pennsylvania west of the Alleghany Mountains, and the Atlantic states 

 south of the Potomac River to western Florida, and westward to the base of the 

 Rocky Mountains from southern Alberta to northern New Mexico; westward passing 

 into the var. occidentalis, Rydb., with deltoid more abruptly acuminate and more 

 coarsely toothed leaves with longer points, and broader at the base, and the com- 

 mon Cottonwood in the region along the eastern base of the Rocky Mountains from 

 Alberta to New Mexico and through western Texas. Comparatively rare and of 

 smaller size in the east and in the coast region of the' south Atlantic and east Gulf 

 states, and the largest and one of the most abundant trees along the streams between 

 the Appalachian and the Rocky Mountains, marking their course over the midconti- 

 nental plateau to the extreme limit of tree-growth, and growing to its largest size as 

 far west as the 100th meridian. 



Often planted for shelter and ornament on the treeless plains and prairies between 

 the Mississippi River and the Rocky Mountains, and as an ornamental tree in the 

 eastern United States, and largely in western and northern Europe. 



10. Populus Fremontii, Wats. Cottonwood. 



Leaves deltoid or reniform, generally contracted into broad short entire points, 

 or rarely rounded or emarginate at the apex, truncate, Jightly cordate or abruptly 

 wedge-shaped at the entire base, coarsely and irregularly serrate, with few or many 

 incurved gland-tipped teeth, coated like the petioles when they unfold with short 

 spreading caducous pubescence, at maturity thick and firm, bright green and lus- 

 trous, 2'-2' long, 2'-3' broad, with thin yellow midribs and 4 or 5 pairs of slender 

 veins; their petioles flattened, yellow, l'-3' long. Flowers: staminate aments 

 densely flowered, l'-2' long, nearly \' broad, with slender glabrous stems; the 

 pistillate sparsely flowered, with stout glabrous or puberulous stems, 2' long, becom- 



