1. [Acer glabrum] Torr. Dwarf Maple.
Leaves glabrous, thin, rounded in outline, cordate-truncate or cuneate at base, 3—5-lobed, the middle lobe usually narrowed and entire below the middle, or often 3-parted or 3-foliolate (f. trisecta Sarg.), with acute or obtuse doubly serrate lobes, 3′—5′ in diameter, dark green and lustrous on the upper, paler on the lower surface, with conspicuous veinlets; petioles stout, grooved, 1′—6′ in length, and often bright red. Flowers about ⅛′ long on short slender pedicels, in loose few-flowered glabrous racemose corymbs on slender drooping peduncles from the end of 2-leaved branchlets, the staminate and pistillate usually produced separately on different plants; sepals oblong, obtuse, petaloid, as long as the greenish yellow petals; stamens 7 or 8, with glabrous unequal filaments shorter than the petals, much shorter or rudimentary in the pistillate flower; ovary glabrous, with short obtuse lobes, rudimentary or 0 in the staminate flower; style divided to the base into 2 spreading stigmatic lobes as long as the petals. Fruit glabrous, with broad nearly erect or slightly spreading wings ¾′—⅞′ long, often rose-colored during the summer; seeds ovoid, bright chestnut-brown, about ¼′ long.
A small tree, occasionally 20°—30° high, with a short trunk 6′—12′ in diameter, small upright branches, and slender glabrous branchlets often slightly many-angled, pale greenish brown when they first appear, becoming bright red-brown during their first winter; often a shrub. Winter-buds acute, ⅛′ long, with bright red or occasionally yellow scales, those of the inner ranks pale brown tinged with pink, tomentose on the inner surface, becoming 1½′ long and narrow-spatulate. Bark of the trunk thin, smooth, and dark reddish brown. Wood heavy, hard, close-grained, light brown or often nearly white, with thick lighter colored sapwood.
Distribution. Borders of mountain streams usually at elevations of 5000°—6000°; Rocky Mountains from Montana to Wyoming, the Black Hills of South Dakota, Sioux County, Nebraska, Colorado, Utah, Nevada, northern Arizona, and to the Sacramento Mountains, New Mexico; in California from the Siskiyou Mountains along the Sierra Nevada to the East Fork of the Kaweah River, Kern County, at altitudes of 5000°—6000° at the north and of 8000°—9000° at the south. Passing into
Acer glabrum var. Douglasii Dippel.
Acer Douglasii Hook.
Leaves ovate or oblong-ovate, slightly cordate by a wide shallow sinus, truncate or rarely rounded at base, 3-lobed with acuminate lobes often slightly divided into acuminate lobules, the terminal leaflet usually ovate from a broad base, or occasionally gradually narrowed below and rhombic in outline and sharply serrate to the base or nearly to the base of the lobe with long-acuminate teeth pointing forward, dark green above, paler and often glaucescent below, 3½′—4′ long and 3′—4′ wide, with 3 prominent nerves extending to the points of the lobes, and slender veins; petioles glabrous, 1′—3½′ in length. Flowers as in the species. Fruit with erect or nearly erect wings, ¾′—1′ long and ⅓′—½′ wide.
A tree, occasionally 40° high, with a short trunk 12′—18′ in diameter, small upright branches and slender bright red-brown branchlets.