SALICACEA, SILVA OF NORTH AMERICA. 73 
POPULUS MEXICANA. 
Cottonwood. 
PIsTILLATE flowers short-pedicellate, their disk large and cup-shaped. Leaves 
rhombic to broadly deltoid, elongated, acute or acuminate, green on both surfaces. 
Populus Mexicana, Wesmael, De Candolle Prodr. xvi. pt. Brewer & Watson, Bot. Cal. ii. 92 (in part). — Rusby, 
ii, 328 (1868) ; Mém. Soc. Sci. Hainaut, sév. 3, iii. 240, Bull. Torrey Bot. Club, ix. 79.— Sargent, Forest Trees 
t. 15 (Monogr. Populus). — Hemsley, Bot. Biol. Am. NV. Am. 10th Census U. S. ix. 175 (in part); Silva N. 
Cent. iii. 181. Am. ix. 183 (in part). — Wesmael, Bull. Bot. Soc. Belg, 
Populus Fremontii, Watson, Proc. 4m. Acad. x. 350 (in xxvi. 376 (in part) (Rev. Gen. Populus). 
part) (1875); Am. Jour. Sci. ser. 3, xv. 186 (in part). — 
A tree, sometimes eighty feet in height, with a trunk three or four feet in diameter covered with 
pale gray or nearly white bark deeply divided into broad flat ridges and heavy gracefully spreading and 
ascending branches which form a broad open head. The branchlets are slender, and when they first 
appear they are pale green and more or less pubescent or villose, with long matted hairs, but soon become 
glabrous and are light yellow-brown during their first season. The terminal winter-buds are narrow, 
acute, light orange-brown, puberulous toward the base of the outer scales, about one quarter of an inch 
long, and two or three times as large as the much compressed oblong lateral buds. The leaves are 
thombic and long-pointed, especially when the tree is young, or broadly deltoid and acute or acuminate 
particularly on vigorous shoots, broadly or acutely cuneate or truncate or slightly cordate at the base, or 
often rounded at the apex and much broader than long, usually coarsely and irregularly crenulate-serrate 
except at the base and towards the apex, and finely crenulate-serrate above the middle when the leaves 
are broad and rounded; when they first unfold the leaves are dark red covered on the lower surface 
with pale pubescence, puberulous on the upper surface, ciliate on the margins, with short white crowded 
hairs, and glandular on the tips of the teeth, with bright red caducous glands; soon becoming glabrous, 
at maturity they are subcoriaceous, bright yellow-green, very lustrous, two or three inches long and 
somewhat narrower or much broader than long, with slender yellow midribs, obscure primary veins, 
coarse reticulate veinlets, and slender nearly terete petioles grooved on the upper side near the base, at 
first puberulous, soon glabrous, and from an inch and a half to nearly two inches in length. The 
stipules are ovate, acute or acuminate, scarious, villose, from one sixteenth to one eighth of an inch long, 
and caducous. The flowers appear before the leaves late in February or early in March, the staminate 
in dense cylindrical aments usually from an inch to an inch and a half in length, the pistillate in 
slender many-flowered aments from an inch and a half to two inches long. The ovary is ovate, rounded 
at the apex, slightly three or four-angled, short-pedicellate, and nearly inclosed in the cup-shaped 
membranaceous disk. The fruiting aments are three or four inches long, and the capsules are borne 
on short stout pedicels thickly placed on the rachis, and are round-ovoid, buff color, slightly three or 
four-lobed, deeply pitted, thin-walled, about one third of an inch long, and surrounded at the base by 
the much enlarged disk.’ 
1 Populus Mexicana is very closely related to the California may be found desirable to treat this north Mexican tree as a variety 
Populus Fremontii, differing chiefly from that species in the larger _ of the California species. : 
disk of the pistillate flowers, in the rhombic leaves which are com- Populus Mexicana is the common Cottonwood of northern Mex- 
mon on young plants, and appear frequently on the same branch ico, and it is this tree which is planted in the streets of Mexican 
with broad deltoid leaves, and in its distribution; and when the cities. (See Pringle, Garden and Forest, i.105 f.) It is also the 
Poplars of the southwest are better known than they are now it common Cottonwood of the valleys of southern Arizona and south- 
