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 rarely opening in the autumn from aments of the year, 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, and 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, ovoid 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 vulgaris Hill., a common European, north African, and Asiatic timber-tree, was introduced many years ago into the northeastern 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.
CONSPECTUS OF THE NORTH AMERICAN ARBORESCENT SPECIES.
Flowers opening in spring with or after the leaves; stamens 4; pistillate aments inclosed during the winter; wing of the nut broad; leaves ovate, sinuately lobed, lustrous on the lower surface.1. [A. sinuata] (B, F, G). Flowers opening in winter or early spring before the unfolding of the leaves; pistillate aments usually naked during the winter. Wing of the nut broad; leaves ovate or elliptic, rusty-pubescent on the lower surface; pistillate aments often inclosed during the winter; stamens 4.2. [A. rubra] (B, G). Wing of the nut reduced to a narrow border. Stamens 4; leaves oblong-ovate, glabrous or puberulous on the lower surface.3. [A. tenuifolia] (B, F, G). Stamens usually 2, or 3. Leaves ovate or oval.4. [A. rhombifolia] (B, F, G). Leaves oblong-lanceolate, acute.5. [A. oblongifolia] (H). Flowers opening in autumn from aments of the year; stamens 4; wing of the nut reduced to a narrow border; leaves oblong-ovate or obovate, dark green and lustrous above, pale yellow-green below.6. [A. maritima] (A).
1. [Alnus sinuata] Rydb. Alder.
Alnus sitchensis Sarg.
Leaves ovate, acute, full and rounded and often unsymmetrical and somewhat oblique or abruptly narrowed and cuneate at base, divided into numerous short acute lateral lobes, sharply and doubly serrate with straight glandular teeth, glandular-viscid as they unfold, at maturity membranaceous, yellow-green on the upper surface, pale and very lustrous on the lower surface, glabrous, or villose along the under side of the stout midrib with short brown hairs also forming tufts in the axils of the numerous slender primary veins, 3′—6′ long, 1½′—4′ wide; petioles stout, grooved, abruptly enlarged at the base, ½′—¾′ in length; stipules oblong to spatulate, rounded and apiculate at apex, puberulous, about ¼′ long. Flowers: staminate aments sessile, in pairs in the axils of the upper leaves sometimes reduced to small bracts, and single in the axil of the leaf next below, during the winter about ½′ long and ⅛′ thick, with dark red-brown shining puberulous apiculate scales, becoming when the flowers open from spring to midsummer 4′ or 5′ long, with a puberulous light red rachis and ovate acute apiculate 3-flowered scales; calyx-lobes rounded, shorter than the 4 stamens; pistillate aments in elongated panicles, inclosed during winter in buds formed the previous summer in the axils of the leaves of short lateral branchlets, long-pedunculate, ⅓′ long, ⅙′ thick. Fruit: strobiles on slender peduncles in elongated sometimes leafy panicles 4′—6′ in length, oblong, ½′—⅝′ long, about ⅓′ thick, their truncate scales thickened at the apex; nut oval, about as wide as its wings.
A tree, sometimes 40° high, with a trunk 7′—8′ in diameter, short small nearly horizontal branches forming a narrow crown, and slender slightly zigzag branchlets puberulous and very glandular when they first appear, bright orange-brown and lustrous and marked by numerous large pale lenticels during their first season, much roughened during their second year by the elevated crowded leaf-scars, becoming light gray. Winter-buds acuminate, dark purple, covered especially toward the apex with close fine pubescence, about ½′ long. Bark thin bluish gray, with bright red inner bark; often a shrub only a few feet tall spreading into broad thickets.
Distribution. Northwest coast from the borders of the Arctic Circle to the high mountains of northern California; common in the valley of the Yukon and eastward through British Columbia to Alberta, and through Washington and Oregon to the western slopes of the Rocky Mountains in Montana; at the north with dwarf Willows, forming great thickets; in southeastern Alaska often a tall tree on rich moist bottom-lands near the mouths of mountain streams, and at the upper limits of tree growth a low shrub; very abundant in the valley of the Yukon on the wet banks of streams and often arborescent in habit; in British Columbia and the United States generally smaller and a shrub, growing usually only at altitudes of more than 3000° above the sea, and often forming thickets on the banks of streams and lakes.
2. [Alnus rubra] Bong. Alder.
Alnus oregona Nutt.
Leaves ovate to elliptic, acute, abruptly or gradually narrowed and cuneate at base, crenately lobed, dentate with minute gland-tipped teeth, and slightly revolute on the margins, covered when they unfold with pale tomentum, at maturity thick dark green and glabrous or pilose with scattered white hairs above, clothed below with short rusty pubescence, 3′—5′ long, 1¾′—3′ wide, or on vigorous branchlets sometimes 8′—10′ long, with a broad midrib and primary veins green on the upper side and orange-colored on the lower, the primary veins running obliquely to the points of the lobes and connected by conspicuous slightly reticulate cross veinlets; petioles orange-colored, nearly terete, slightly grooved, ¼′—¾′ in length; stipules ovate, acute, pale green flushed with red, tomentose, ⅛′—¼′ long. Flowers: staminate aments in red-stemmed clusters, during the winter 1¼′ long, ⅛′ thick, with dark red-brown lustrous closely appressed scales, becoming 4′—6′ long and ¼′ thick, with ovate acute orange-colored glabrous scales; calyx yellow, with ovate rounded lobes rather shorter than the 4 stamens; pistillate aments in short racemes usually inclosed during the winter in buds formed during the early summer and opening in the early spring, ⅓′—½′ long, about 1/16′ thick, with dark red acute scales; styles bright red. Fruit: strobiles raised on stout orange-colored peduncles sometimes ½′ in length, ovoid or oblong, ½′—1′ long, ⅓′—½′ thick, with truncate scales much thickened toward the apex; nut orbicular to obovoid, surrounded by a membranaceous wing.
A tree, usually 40°—50°, occasionally 90° high, with a trunk sometimes 3° in diameter, slender somewhat pendulous branches forming a narrow pyramidal head, and slender branchlets marked by minute scattered pale lenticels, light green and coated at first with hoary tomentum sometimes persistent until their second year, becoming during the first winter bright red and lustrous and ultimately ashy gray. Winter-buds about ⅓′ long, dark red, covered with pale scurfy pubescence. Bark rarely more than ¾′ thick, close, roughened by minute wart-like excrescences, pale gray or nearly white, with a thin outer layer, and bright red-brown inner bark. Wood light, soft, brittle, not strong, close-grained, light brown tinged with red, with thick nearly white sapwood; in Washington and Oregon largely used in the manufacture of furniture and for smoking salmon; by the Indians of Alaska the trunks are hollowed into canoes.
Distribution. Shores of Yakutat Bay, southeastern Alaska, southward near the coast to the cañons of the Santa Inez Mountains, Santa Barbara County, California; common along the banks of streams, and of its largest size near the shores of Puget Sound; in California most abundant in Mendocino, Humboldt and Marin Counties, forming groves on bottom-lands near the coast; often ranging inland for 20 or 30 miles, and occasionally ascending to altitudes of 2000° above the sea.
3. [Alnus tenuifolia] Nutt. Alder.
Leaves ovate-oblong, acute or acuminate, broad and rounded or cordate or occasionally abruptly narrowed and cuneate at base, usually acutely laciniately lobed and doubly serrate, when they unfold light green often tinged with red, pilose on the upper surface and coated on the lower with pale tomentum, at maturity thin and firm, dark green and glabrous above, pale yellow-green and glabrous or puberulous below, 2′—4′ long, 1½′—2½′ wide, with a stout orange-colored midrib impressed on the upper side, and slender primary veins running to the points of the lobes; petioles stout, slightly grooved, orange-colored, ½′—1′ in length; stipules ovate, acute, thin, and scarious, ½′ long, about ⅛′ wide, covered with pale pubescence. Flowers: staminate aments 3 or 4 in number in slender-stemmed racemes, nearly sessile or raised on stout peduncles often ½′ long, during the winter light purple, ¾′—1′ long and ¼′ thick, becoming 1½′—2′ in length; calyx-lobes rounded, shorter than the 4 stamens; pistillate aments naked during the winter, dark red-brown, nearly ¼′ long, with acute apiculate loosely imbricated scales, only slightly enlarged when the flowers open. Fruit: strobiles obovoid-oblong, ⅓′—½′ 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 ¼′—⅓′ long, bright red, and puberulous. Bark rarely more than ¼′ thick, bright red-brown and broken on the surface into small closely appressed scales.
Distribution. Banks of streams and mountain cañons 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 headwaters 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 sometimes coarsely and occasionally doubly serrate, slightly thickened and reflexed on the somewhat 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 puberulous below, 2′—3′ long, 1½′—2′ wide, with a stout yellow midrib and primary veins; petioles slender, yellow, hairy, flattened and grooved on the upper side, ½′—¾′ long; stipules ovate, acute, scarious, puberulous, about ¼′ in length. Flowers: staminate aments in slender-stemmed pubescent clusters, usually short-stalked, during the summer dark olive-brown and lustrous, ¾′—1′ long and about 1/16′ thick, beginning to lengthen late in the autumn before the leaves fall, fully grown and 4′—6′ long and ¼′ thick in January, with dark orange-brown scales, and deciduous in February before the appearance of the new leaves; calyx yellow, 4-lobed, rather shorter than the 2 or occasionally 3 or rarely single stamen; pistillate aments in short pubescent racemes emerging from the bud in December, their scales broadly ovate and rounded. Fruit: strobiles oblong, ⅓′—½′ long, with thin scales slightly thickened and lobed at apex, fully grown at midsummer, remaining closed until the trees flower the following year; nut broadly ovoid, with a thin margin.
A tree, frequently 70°—80° high, with a tall straight trunk 2°—3° in diameter, long slender branches pendulous at the ends, forming a wide round-topped open head, and slender branchlets marked by small scattered lenticels, at first light green and coated with pale caducous pubescence, soon becoming dark orange-red and glabrous, and darker during the winter and following summer. Winter-buds nearly ½′ long, very slender, dark red, and covered with pale scurfy pubescence. Bark on old trunks 1′ thick, dark brown, irregularly divided into flat often connected ridges broken into oblong plates covered with small closely appressed scales. Wood light, soft, not strong, brittle, close-grained, light brown, with thick lighter colored often nearly white sapwood.
Distribution. Banks of streams from northern Idaho to the eastern slope of the Cascade Mountains of Washington and southeastern Oregon, and southward from the valley of the Willamette River, Oregon (near Salem, Marion County, J. C. Nelson) over the coast ranges and along the western slopes of the Sierra Nevada to the mountains of southern California (San Bernardino, San Jacinto, and Cuyamaca Ranges); the common Alder of the valleys of central California, occasionally ascending on the southern Sierra Nevada to altitudes of 8000°, and the only species at low altitudes in the southern part of the state.
5. [Alnus oblongifolia] Torr. Alder.
Alnus acuminata Sarg., not H. B. K.
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.
Leaves oblong-ovate, or obovate, acute, acuminate or rounded at apex, gradually narrowed and cuneate at base, remotely serrate with minute incurved glandular teeth, and somewhat thickened on the slightly undulate margins, when they unfold, light green tinged with red, hairy on the midrib, veins, and petioles, and coated above with pale scurfy pubescence, at maturity dark green, very lustrous, and covered below by minute pale glandular dots, 3′—4′ long, 1½′—2′ wide, with a stout yellow midrib and primary veins prominent and glandular on the upper side and slightly puberulous below; petioles stout, yellow, glandular, flattened and grooved on the upper side, ½′—¾′ in length; stipules oblong, acute, about ⅛′ long, dark reddish brown, caducous. Flowers opening in the autumn: aments appearing in July on branches of the year and fully grown in August or early in September; staminate in short scurfy-pubescent glandular-pitted racemes on slender peduncles sometimes 1′ in length from the axils of upper leaves, covered at first with ovate acute dark green very lustrous scales slightly ciliate on the margins and furnished at apex with minute red points, at maturity 1½′—2½′ long, ¼′ to nearly ½′ thick, with dark orange-brown scales raised on slender stalks, and 4 bright orange-colored stamens; pistillate usually solitary from the axils of the lower leaves on stout pubescent peduncles, bright red at apex and light green below before opening, with ovate acute scales slightly ciliate on the margins, about ⅛′ long when the styles protrude from between the scales, beginning to enlarge the following spring. Fruit attaining full size at midsummer and then raised on a stout peduncle, broadly ovoid, rounded and depressed at base, gradually narrowed to the rather obtuse apex, about ⅝′ long and ½′ broad, with thin lustrous scales slightly thickened and crenately lobed at apex, turning dark reddish brown or nearly black and opening late in the autumn and remaining on the branches until after the flowers open the following year; nut oblong-obovoid, gradually narrowed and apiculate at apex, with a thin membranaceous border.
A tree, occasionally 30° high, with a tall straight trunk 4′—5′ in diameter, small spreading branches forming a narrow round-topped head, slender slightly zigzag branchlets, light green and hairy at first, pale yellow-green, very lustrous, slightly puberulous, marked with occasional small orange-colored lenticels, and glandular with minute dark glandular dots during their first summer, becoming dull light orange or reddish brown in the winter, and ashy gray often slightly tinged with red the following season; more often shrubby, with numerous slender spreading stems 15°—20° tall. Winter-buds acute, dark red, coated with pale lustrous scurfy pubescence, about ¼′ long. Bark ⅛′ thick, smooth, light brown or brown tinged with gray. Wood light, soft, close-grained, light brown, with thick hardly distinguishable sapwood.
Distribution. Banks of streams and ponds in southern Delaware and Maryland, and in south central Oklahoma (Johnson and Bryan Counties).
Occasionally cultivated as an ornamental tree in the eastern states and hardy as far north as Massachusetts.