TREES OF NORTH AMERICA 



and j' thick, becoming l^'-2' in length; calyx-lobes rounded, shorter than the 4 stamens; 

 pistillate aments naked during the winter, dark red-brown, nearly \' long, with acute apic- 

 ulate loosely imbricated scales, only slightly enlarged when the flowers open. Fruit: 

 strobiles obovoid-oblong, \'-% r long, their scales much thickened, truncate and 3-lobed at 

 apex; nut nearly circular to slightly obovoid, surrounded by a thin membranaceous border. 



A tree, occasionally 30 tall, with a trunk 6 '-8' in diameter, small spreading slightly 

 pendulous branches forming a narrow round-topped head, and slender branchlets marked 

 at first by a few large orange-colored lenticels and coated with fine pale or rusty caducous 

 pubescence, becoming light brown or ashy gray more or less deeply flushed with red in their 

 first winter and ultimately paler; more often shrubby, with several spreading stems, and 

 at the north and at high altitudes frequently only 4-5 tall. Winter-buds \'-\' long, 

 bright red, and puberulous. Bark rarely more than \' thick, bright red-brown and broken 

 on the surface into small closely appressed scales. 



Distribution. Banks of streams and mountain canons from Francis Lake in latitude 

 61 north to the valley of the lower Fraser River, British Columbia, eastward along the 

 Saskatchewan to Prince Albert, and southward through the Rocky Mountains to northern 

 New Mexico; on the Sierra Nevada of southern California, and in Lower California; the 

 common Alder of mountain streams in the northern interior region of the continent; very 

 abundant on the eastern slopes of the Cascade Mountains, and on the southern California 

 Sierras; forming great thickets at 6000-7000 above the sea along the head-waters of the 

 rivers of southern California flowing to the Pacific Ocean; the common Alder of eastern 

 Washington and Oregon, and of Idaho and Montana; very abundant and of its largest size 

 in Colorado and northern New Mexico. 



4. Alnus rhombifolia Nutt. White Alder. Alder. 



Leaves ovate or oval or sometimes nearly orbicular, rounded or acute at apex, especially 

 on vigorous shoots, gradually or abruptly narrowed and cuneate at base, finely or some- 

 times coarsely and occasionally doubly serrate, slightly thickened and reflexed on the some- 



Fig. 212 



what undulate margins, when they unfold pale green and covered with deciduous matted 

 white hairs, at maturity dark green and lustrous on the upper surface, frequently marked, 

 especially on the midrib, with minute glandular dots, light yellow-green and slightly puber- 

 ulous below, 2'-3' long, l|'-2' wide, with a stout yellow midrib and primary veins; peti- 

 oles slender, yellow, hairy, flattened and grooved on the upper side, f '- f' long; stipules 

 ovate, acute, scarious, puberulous, about \' in length. Flowers: staminate aments in 

 slender-stemmed pubescent clusters, usually short-stalked, during the summer dark olive- 



