SALICACE.E 131 



scales, the terminal usually about \' long and usually two or three times as large as the 

 lateral buds. Bark on young stems light gray-brown, thin, smooth or slightly fissured, 

 becoming on old trees l|'-2' thick, dark brown slightly tinged with red, and deeply and 

 irregularly divided into broad connected rounded ridges covered with small closely ap- 

 pressed scales. Wood light brown, with thin nearly white sapwood. 



Distribution. Banks of streams; valley of the upper Sacramento River southward 

 through western California to the San Pedro Martir Mountains, Lower California; most 

 abundant in the San Joaquin Valley, and ascending the western slopes of the southern 

 Sierra Nevada to altitudes of 3000. 



Often planted in southern California as a shade-tree, and for the fuel produced quickly 

 and abundantly from pollarded trees. 



In San Bernardino and San Diego Counties, California, generally replaced by the var. 

 pubescens Sarg., differing in its pubescent branchlets and ranging eastward to southwestern 

 Nevada and southern Utah. In southern Arizona and near Silver City, Grant County, 

 New Mexico, represented by the var. Thornberii Sarg., differing from the typical P. Fre- 

 montii in the more numerous serratures of the leaves, in the ellipsoidal not ovoid capsules 

 with smaller disk and shorter pedicels, and by the var. Toumeyi Sarg., differing from the 

 type in the shallow cordate base of the leaves, gradually narrowed and cuneate to the in- 

 sertion of the petiole, and in the larger disk of the fruit (Fig. 124). The var. macrodisca 

 Sarg. with a broad disc nearly inclosing the ellipsoidal fruit is known only in the neigh- 

 borhood of Silver City. 



X Populus Parryi Sarg., a probable hybrid of P. Fremontii and P. trichocarpa, with char- 

 acters intermediate between those of its supposed parents, grows naturally along Cotton- 

 wood Creek on the west side of Owens Lake, Inyo County, and in the neighborhood of 

 Fort Tejon, Kern County, and as a street tree is not rare in San Bernardino, California. 



9. Populus arizonica Sarg. Cottonwood. 



Populus mexicana Sarg. not Wesm. 



Leaves deltoid or reniform, gradually or abruptly long-pointed at the acuminate entire 

 apex, truncate or broad-cuneate at the wide base, finely serrate with numerous teeth, as 



Fig. 125 



they unfold dark red covered below with pale pubescence, pubescent above, ciliate on 

 the margins, thin, glandular with bright red caducous glands, soon becoming glabrous, at 



