or deltoid-subreniform, mostly abruptly narrowed and acuminate-attenuate at 

 the entire apex, truncate to shallowly cordate or sometimes widely cuneate at 

 base, the margins coarsely serrate with usually less than 10 teeth on each side, 

 provided with two small glands at juncture with petioles, 7-11 cm. long, usually 

 about as broad as or broader than long; petioles slender, laterally compressed, 

 5-10 cm. long; pistillate aments 6-13 cm. long, with mature pedicels 1-6 (rarely 

 more) mm. long (usually 5 mm. or less) and shallow disks 2-4 mm. in diameter; 

 floral bracts caducous, thin, scarious, cuneate below, dilated above and lacerate 

 on the apical margin, 3-4 mm. long; fruits broadly ovoid to ovoid-ellipsoidal, 

 pitted, 1-1.5 cm. long, 3- to 4-valved; seeds ellipsoid, usually widest above the 

 middle, apiculate, compressed, 3-4 mm. long. P. deltoides [var.] occidentalis Rydb. 



In sandy alluvial soils along rivers and streams, about stock tanks and along 

 roadside banks scattered over the Tex. Plains Country from Nolan Co. northw., 

 and extending over into Cooke and Montague cos. in n.-cen. Tex. and into Okla., 

 Mar.-June; from s. Sask., s. Alta. and S.D., s. to w. Okla., n. Tex. and n.e. N.M. 



When in fruit, var. Sargentii is readily distinguished from both P. deltoides 

 and P. Wislizenii by its short pedicels which are shorter than the fruits and usually 

 less than 5 mm. long. From P. deltoides it is also distinguished by its pubescent, 

 not glabrous, buds, and from P. Wislizenii by the glands that are developed at 

 the junction of the leaf blades and petioles. The glands are smaller and of a 

 different shape than those of P. deltoides. 



Var. texana (Sarg.) Correll. Texas cottonwood. P. texana Sarg. Variety 

 texana occurs in the same types of habitat and, in Texas and Oklahoma, occupies 

 approximately the same area of distribution as var. Sargentii. 



Except for the fact that var. texana rarely, if ever, has glands at the junction 

 of the leaf blades and petioles it could be referred to var. Sargentii. This lack 

 of well-developed glands is apparently the only characteristic that separates these 

 two entities. Sterile specimens of var. texana resemble P. Wislizenii so closely 

 that if it were not for a difference in their area of distribution it would prac- 

 tically be impossible to distinguish one from the other. The leaves of var. texana, 

 however, usually have a more abruptly acuminate-attenuate apex, and some of 

 the leaves occasionally have one or two abortive glands, a characteristic that is 

 not evident in P. Wislizenii. In fruit, however, the stout pedicels of var. texana, 

 which rarely exceed 5 mm. in length, conveniently separate it from the longer, 

 more slender pedicels of P. Wislizenii. 

 8. Populus tremuloides Michx. Quacking aspen, alamo temblon. Fig. 386. 



Tree (in our area) rarely more than 15 m. tall, attaining a much greater size 

 at lower elevations, with a slender erect trunk to about 1.5 dm. in diameter, 

 the slender pendulous branches forming a narrow symmetrical domelike crown; 

 bark smooth, firm, grayish-white to brownish or pale-green occasionally mottled 

 with yellow, with scattered black rounded protuberances and curved scarlike 

 marks, the older bark at base of trunk irregularly fissured and becoming blackish; 

 branchlets slender, flexible, glabrous and shiny, reddish-brown in autumn of first 

 year, later becoming gray, provided with scattered elliptic orange-colored lenticels; 

 buds reddish-brown, shiny, slightly resinous, ellipsoid-conic, sharp-pointed, some- 

 times with the lowermost scales slightly puberulent, to about 1 cm. long; leaf 

 blades glabrous, suborbicular to orbicular-ovate or sometimes orbicular-subreni- 

 form, abruptly apiculate to shortly acuminate at apex, truncate to broadly rounded 

 or shallowly cordate at base, deep-yellowish-green and lustrous on upper surface, 

 paler on lower surface, with conspicuous yellowish veins, becoming yellowish to 

 deep orange-color in autumn, the margins regularly and finely crenulate-serrulate, 

 occasionally with small glands at juncture with petiole to 7.5 cm. long, frequently 

 wider than long; petiole slender, weak, yellow, laterally compressed just below the 



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