Distribution. Banks of streams and springs, San Bernardino County, California (Cottonwood Springs, Meca, etc.), and eastward to the bottoms of the Colorado River from Clark County, Nevada, to Yuma, Arizona, and probably the only Cottonwood in this arid region. Often planted as a street tree in the towns of southwestern California and of adjacent Nevada and Arizona. 12. Populus Wislizenii Sarg. Cottonwood. [Illustration: Fig. 128] Leaves broadly deltoid, abruptly short- or long-pointed at apex, truncate or sometimes cordate at the broad entire base, coarsely and irregularly crenately serrate except toward the entire apex, coriaceous, glabrous, yellow-green and lustrous, 2′—2½′ long, usually about 3′ wide, with a slender yellow midrib, thin remote primary veins and conspicuous reticulate veinlets; petioles slender, glabrous, 1½′—2′ long; on vigorous shoots often 3½′—4′ long and wide with petioles 3½′—4′ in length. Flowers: aments 2′—4′ long, the pistillate becoming 4′—5′ long before the fruit ripens; scales scarious, light red, divided at the apex into elongated filiform lobes; disk of the staminate flower broad and oblique; stamens numerous, with large oblong anthers and short filaments; disk of the pistillate flower cup-shaped, irregularly dentate, inclosing to the middle the long stalked ovary full and rounded at apex, with 3 broad crenulate lobed stigmas raised on the short branches of the style. Fruit oblong-ovoid, thick-walled, acute, 3 or 4-valved, slightly ridged, buff color, ¼′ long; pedicels slender, ½′—¾′ in length and placed rather remotely on the slender glabrous rachis of the ament. A large tree, with wide-spreading branches, and stout light orange-colored glabrous branchlets. Winter-buds acute lustrous, puberulous. Bark pale gray-brown, deeply divided into broad flat ridges. Wood used as fuel, for fence-posts and the rafters of Mexican houses. Distribution. Western Texas through New Mexico to the valley of Grand River, western Colorado (Grand Junction, Mesa County); common in the valley of the Rio Grande in western Texas and New Mexico, and the adjacent parts of Mexico. Often planted as a shade tree in New Mexico. 13. Populus Sargentii Dode. _Populus deltoides_ var. _occidentalis_ Rydb. [Illustration: Fig. 129]