eels 7-15 (rarely less) mm. long and shallow disks 3-4 mm. in diameter; fruits 

 broadly ovoid-ellipsoid to ovoid-conic or suborbicular, pitted, 8-18 mm. long, 

 rarely smaller, 3- or 4-valved; seeds ellipsoid, apiculate, compressed, 3-4 mm. long. 



Along rivers, streams and irrigation canals in valleys and canyons, in rocky 

 or deep alluvial soils, in the Tex. Trans-Pecos, Mar.-July; from s. Colo, and s. 

 Ut., s. to w. Tex., N.M. and n. Mex. 



This is the common cottonwood along the Rio Grande in extreme west Texas 

 and New Mexico. It is separated from P. Fremontii, which it resembles, not only 

 by an apparent difference in distribution but also by its relatively narrower 

 capsules and much longer pedicels. 



6. Populus deltoides Marsh. Eastern cottonwood, alamo. Fig. 384. 



Tree to 30 m. or more tall, with a large erect trunk to 2 m. or more in diameter, 

 the branches often massive and erect-spreading or gradually wide-spreading to be- 

 come pendulous at their extremities and form a wide open crown that occasionally 

 attains a spread of 30 m. or more in diameter; bark ashy-gray, thick, deeply 

 fissured to form broad rounded ridges; branchlets usually stout, glabrous, terete 

 or angular, light-yellowish-green to brownish or grayish, when young commonly 

 sparsely hispid; buds large, ovoid to ellipsoid, acute, resinous, bright-reddish- 

 brown, glabrous, 1.2-3 cm. long; leaf blades thick and coriaceous, rarely thihnish, 

 pale bright- or grayish-green and shiny on the upper surface, paler on the lower 

 surface, turning a bright clear-yellow in autumn, deltoid to deltoid-ovate or 

 suborbicular-ovate, abruptly or gradually triangular-acuminate (often attenute) 

 or occasionally rounded and acute-apiculate at apex, truncate to cordate or 

 broadly rounded to rarely somewhat broadly cuneate at base, the margins 

 crenately serrate with few coarse or many fine teeth that are commonly ciliate, 

 with 2 or more enlarged conspicuous glands at juncture with petioles, glutinous 

 and fragrant of balsam when young and provided with white caducous hairs, 

 7-15 cm. long, usually about as wide as long or longer than wide; petioles slender, 

 pilose at first but soon glabrous, yellowish or tinged with red, laterally compressed, 

 to 15 cm. long; staminate aments densely flowered, cylindric, 7-10 cm. long, with 

 pedicels 8-10 mm. long and oblique disks 3-4 mm. in diameter, the disks sup- 

 porting about 60 stamens with anthers about 1 mm. long; pistillate aments laxly 

 flowered, to 2 dm. or more long, with mature pedicels 8-13 (rarely less) mm. 

 long and shallow cup-shaped disks 2.5-3 mm. in diameter; floral bracts caducous, 

 glabrous, light-brown, narrowly to broadly cuneate, sometimes 3-lobed, irregularly 

 lacerate on the margins of the upper half, 2.5-5.5 mm. long; fruits ellipsoid-conic 

 to suborbicular-ovoid, sharp-pointed, somewhat pitted, 6-15 mm. long, 3- to 

 4-valved; seeds ellipsoid-obovoid, apiculate, compressed, 3-4 mm. long. 



Occurring naturally in Tex. as far n.w. as the s. Plains Country and s.w. 

 to Uvalde Co. in the Rio Grande Plains, and Okla. {^Waterfall), Mar.-July; from 

 N.H. s. to n.w. Fla., w. to s. Sask., N.D., w. Kan., w. Okla. and Tex. 



This species may be found along practically every watercourse of any size 

 and about most of the springs and waterholes in the eastern third of Texas, 

 commonly planted along roadways and about dwellings, growing especially well in 

 deep alluvial soils. 



7. Populus Sargentu Dode var. Sargentii. Plains cottonwood. Fig. 385. 



Tree 8-27 m. tall, with a heavy trunk up to about 1.5 m. in diameter, the 

 branches large and spreading-pcndulous to form a broad open crown; bark 

 grayish, becoming darker with age, thick, deeply fissured to form broad ridges; 

 branchlets slender, pale yellowish brown or sometimes grayish, glabrous; buds 

 ellipsoid-conic, sharp-pointed somewhat resinous, yellowish brown, puberulent 

 to somewhat hirsute, 1-2.5 cm. long; leaf blades firm, yellowish green and shiny 

 on the upper surface, paler on the lower surface, broadly deltoid to deltoid-ovate 



748 



