5. Alnus oblongifolia Torr. Alder. _Alnus acuminata_ Sarg., not H. B. K. [Illustration: Fig. 213] Leaves oblong-lanceolate, acute; or rarely obovate and rounded at apex, gradually narrowed and cuneate at base, sharply and usually doubly serrate, more or less thickly covered, especially early in the season, with black glands, dark yellow-green and glabrous or slightly puberulous above, pale and glabrous or puberulous below, especially along the slender yellow midrib and veins, with small tufts of rusty hairs in the axils of the primary veins, 2′—3′ long, about 1½′ wide; petioles slender, grooved, pubescent, ¾′ long; stipules ovate-lanceolate, brown and scarious, about ¼′ in length. Flowers: staminate aments in short stout-stemmed racemes, during the winter light yellow, ½′—¾′ long and about 1/16′ thick, becoming when the flowers open at the end of February before the appearance of the leaves 2′—2½′ in length, with ovate pointed dark orange-brown scales; calyx 4-lobed; stamens 3 or occasionally 2, with pale red anthers soon becoming light yellow; pistillate aments naked during the winter, ⅛′ to nearly ¼′ long, with light brown ovate rounded scales; stigmas bright red. Fruit: strobiles ½′—1′ long, with thin scales slightly thickened and nearly truncate at apex; nut broadly ovoid, with a narrow membranaceous border. A tree, in the United States rarely more than 20°—30° high, with a trunk sometimes 8′ in diameter, long slender spreading branches forming an open round-topped head, and slender branchlets slightly puberulous when they first appear, light orange-red and lustrous during their first winter, and marked by small conspicuous pale lenticels, becoming in their second year dark red-brown or gray tinged with red and much roughened by the elevated leaf-scars. Winter-buds acute, red, lustrous, glabrous, ½′ long. Bark thin, smooth, light brown tinged with red. Distribution. Banks of streams in cañons of the mountains of southern New Mexico and Arizona at altitudes of 4000°—6000° above the sea; in Oak Creek Cañon near Flagstaff, northern Arizona (tree 100° × 3°, _P. Lowell_); and on the mountains of northern Mexico. 6. Alnus maritima Nutt. Alder. [Illustration: Fig. 214]