12. [Salix exigua] Nutt.
Leaves lanceolate to oblanceolate, acuminate at the ends, often slightly falcate, minutely glandular-serrate above the middle, bluish green and glabrous above, covered below with appressed silky white hairs, 1½′—3′ long, ⅛′—¼′ wide, or on summer shoots sometimes 4½′ long and 1½′ wide; petioles glabrous, 1/16′ long or less; stipules minute or wanting. Flowers: aments terminal and solitary or terminal and axillary, on leafy glabrous branchlets, 1′—2′ in length; scales hoary pubescent, lanceolate and acute on staminate aments, often wider, obovate and rounded at the apex on pistillate aments; stamens, 2, filaments hairy below the middle; ovary sessile, villose, the stigmatic lobes sessile. Fruit ovoid, acuminate, glabrous.
A shrub with stems 10° or 12° tall, or rarely a tree 25° high, with a trunk 5′ or 6′ in diameter, thin spreading branches forming a round-topped head, and slender glabrous red-brown branchlets. Bark of the trunk thin, longitudinally fissured, grayish brown.
Distribution. Southern Alberta and valley of the Fraser River (Clinton), British Columbia, southward through western Washington and Oregon to San Diego County, California, and southeastern Nevada, and eastward to southern Idaho, central Nevada and western Wyoming (Yellowstone National Park).
Apparently only truly a tree on the banks of the Palouse and other streams of eastern Washington.
Several shrubby forms of S. exigua found in Nevada, Arizona, Colorado, western Nebraska and in Lower California are distinguished.
13. [Salix longifolia] Muehl. Sand Bar Willow.
Salix fluviatalis Sarg., not Nutt.
