208 TREES OF NORTH AMERICA 



strong, light brown, with thick lighter colored sapwood; sometimes used for fuel and 

 fencing. 



Distribution. Moist soil near the banks of streams in mountain canons; gen- 

 erally distributed, although nowhere very common, from the basin of the upper Fraser 

 and Peace rivers in British Columbia, southward to the valleys of Mt. Shasta and 

 the eastern slopes of the northern Sierra Nevada, California, eastward through 

 Alberta and along the valley of the Saskatchewan, and southward along the Rocky 

 Mountains and the interior ranges of Nevada, Utah, and northern New Mexico, 

 extending eastward in the United States to the Black Hills of Dakota, northwestern 

 Nebraska, and the eastern base of the Rocky Mountains in Colorado. 



4. ALNUS, L. Alder. 



Trees and shrubs, with astringent scaly bark, soft straight-grained wood, naked 

 stipitate winter-buds formed in summer and nearly inclosed by the united stipules 

 of the first leaf, becoming thick, resinous, and dark red. Leaves open and convex 

 in the bud, falling without change of color; stipules of all but the first leaf ovate, 

 acute, and scarious. Flowers vernal or in one species autumnal, in 1-3-flowered 

 cymes in the axils of the peltate short-stalked scales of stalked aments formed in 

 summer or autumn in the axils of the last leaves of the year or of those of minute 

 leafy bracts; staminate aments elongated, pendulous, paniculate, naked and erect 

 during the winter, each staminate flower subtended by 3-5 minute bractlets adnate 

 to the scales .of the ament, and composed of a 4-parted calyx, 1-3 or usually 4 

 stamens inserted on the base of the calyx opposite its lobes, with short simple 

 filaments; pistillate aments ovoid or oblong, erect, stalked, produced in summer in 

 the axils of the leaves of a branch developed from the axils of an upper leaf of the 

 year, and below the staminate inflorescence, inclosed at first in the stipules of 

 the first leaf, emerging in the autumn and naked during the winter, or remaining 

 covered until early spring; pistillate flowers in pairs, each flower subtended by 2-4 

 minute bractlets adnate to the fleshy scale of the ament becoming at maturity 

 thick and woody, obovate, 3-5-lobed or truncate at the thickened apex, forming an 

 ovoid or subglobose strobile persistent after the opening of its closely imbricated 

 scales; calyx 0; ovary compressed; nut minute, bright chestnut-brown, ovate to 

 oblong, flat, bearing at the apex the remnants of the style, marked at the base by 

 a pale scar, the outer coat of the shell produced into lateral wings often reduced 

 to a narrow membranaceous border. 



Alnus inhabits swamps, river bottom-lands, and high mountains, and is widely and 

 generally distributed through the northern hemisphere, often forming the most 

 conspicuous feature of vegetation on mountain slopes, ranging at high altitudes 

 southward in the New World through Central America to Colombia, Peru, and 

 Bolivia, and to upper Assam and Japan in the Old World. Of the eighteen or twenty 

 species now recognized nine are North American ; of these six attain the size and habit 

 of trees. Of the exotic species, Alnus glutinosa, Gaert., a common European, North 

 African, and Asiatic timber-tree, was introduced many years ago into the northeast- 

 ern states, where it has become locally naturalized. The wood of Alnus is very 

 durable in water, and the astringent bark and strobiles are used in tanning leather 

 and in medicine. 



Alnus is the classical name of the Alder. 



