4. SORBUS L. Mountain Ash.
Trees or shrubs, with smooth aromatic bark, stout terete branchlets, large buds covered by imbricated scales, the inner accrescent and marking the base of the branchlet by conspicuous ring-like scars, and fibrous roots. Leaves alternate, pinnate in the American species, the pinnæ conduplicate in the bud, serrate, deciduous; stipules free from the petioles, foliaceous. Flowers in broad terminal leafy cymes; calyx-tube urn-shaped, 5-lobed, the lobes imbricated in the bud, persistent; petals rounded, abruptly narrowed below, white; stamens usually 20 in 3 series, those of the outer series opposite the petals; carpels 2—5, usually 3; styles usually 3, distinct; ovules 2 in each cell, ascending; raphe dorsal; micropyle inferior. Fruit a small subglobose red or orange-red pome with acid flesh, and papery carpels free at the apex. Seeds 2, or by abortion 1, in each cell, ovoid, acute, erect; seed-coat cartilaginous, chestnut-brown and lustrous; embryo erect; cotyledons plano-convex, flat; radicle short, inferior.
Sorbus is widely distributed through the northern and elevated regions of the northern hemisphere with three or four species in North America of which one is arborescent, and with many species in eastern Asia and in Europe. Of the exotic species, Sorbus Aucuparia L., the common European Mountain Ash, or Rowan-tree, with several of its varieties and hybrids, is often cultivated as an ornamental tree in Canada and the northern states and has become sparingly naturalized northward.
Sorbus is the classical name of the Pear or of the Service-tree.
1. [Sorbus americana] Marsh.
Leaves 6′—8′ long, with 13—17 lanceolate acute taper-pointed leaflets unequally cuneate or rounded and entire at base, sharply serrate above with acute often glandular teeth, sessile or short-stalked, or the terminal leaflet on a stalk sometimes ½′ long, when they unfold slightly pubescent below, at maturity membranaceous, glabrous, dark yellow-green, on the upper surface, and paler or glaucescent and rarely pubescent on the lower surface, 2′—4½′ long, ¼′—1′ wide, with a prominent midrib and thin veins; turning bright clear yellow before falling in the autumn; petioles grooved, dark green or red, 2′—3′ in length, the rachis often furnished with tufts of dark hairs at the base of the petiolules; stipules broad, nearly triangular, variously toothed, caducous. Flowers appearing after the leaves are fully grown, ⅛′ in diameter, on short stout pedicels, in flat cymes 3′—4′ across, with acute minute caducous bracts and bractlets; calyx broadly obconic and puberulous, with short, nearly triangular lobes tipped with minute glands and about half as long as the nearly orbicular creamy white petals. Fruit ¼′ in diameter, subglobose or slightly pyriform, bright orange-red, with thin flesh; seeds pale chestnut color, rounded at apex, acute at base, about ⅛′ long.
A tree, 20°—30° high, with a trunk rarely more than a foot in diameter, spreading slender branches forming a narrow round-topped head, and stout branchlets pubescent at first, soon glabrous, becoming in their first winter brown tinged with red, and marked by the large leaf-scars and by oblong pale remote lenticels, and darker in their second year, the thin papery outer layer of bark then easily separable from the bright green fragrant inner layers; more often a tall or sometimes a low shrub, with numerous stems. Winter-buds acute, ¼′—¾′ long, with dark vinous red acuminate scales rounded on the back, more or less pilose, covered with a gummy exudation, the inner scales hoary-tomentose in the bud. Bark ⅛′ thick, with a smooth light gray surface irregularly broken by small appressed plate-like scales. Wood close-grained, light, soft and weak, pale brown, with lighter colored sapwood of 15—20 layers of annual growth. The astringent fruit is employed domestically in infusions and decoctions, and in homœopathic remedies.
Distribution. Borders of swamps and rocky hillsides; Newfoundland to Manitoba and southward through the maritime provinces of Canada, Quebec and Ontario, the elevated portions of the northeastern United States and the region of the Great Lakes to Minnesota, and on the Appalachian Mountains from western Pennsylvania and West Virginia to North Carolina and Tennessee; in North Carolina ascending to altitudes of nearly 6000°; probably of its largest size on the northern shores of Lakes Huron and Superior; in the United States, except in New England, more often a shrub than a tree; on the Appalachian Mountains usually low, with narrower leaflets and smaller fruit than northward.
Often cultivated in Canada and the northeastern States for the beauty of its fruit and the brilliancy of its autumn foliage. Of its forms the most distinct is
Sorbus americana var. decora Sarg.
Pyrus sambucifolia A. Gray, not Cham. and Schlecht.
Pyrus americana var. decora Sarg.
Sorbus decora Schn.
Sorbus scopulina Britt., in part, not Greene.
Pyrus sitchensis Rob. and Fern., not Piper.
Leaves 4′—6′ long, with 7—13 oblong-oval to ovate-lanceolate leaflets blunt and rounded, abruptly short-pointed or acuminate at apex, pubescent below as they unfold, at maturity glabrous, dark bluish green on the upper surface and pale on the lower surface; petioles stout, usually red 1½′—2′ in length. Flowers ¼′ in diameter, in rather narrower clusters, appearing eight to ten days later than those of the type. Fruit subglobose, bright orange-red, often ½′ in diameter.
A tree, occasionally 30° high, with a trunk sometimes a foot in diameter, and spreading branches forming a round-topped handsome head.
Distribution. Coast of Labrador to the northern shores of Lake Superior and Minnesota, southward to the mountains of northern New Hampshire, Vermont, and New York. Distinct in its extreme forms but connected with Sorbus americana by intermediate forms.
This variety of Sorbus americana, perhaps the most beautiful of the genus when the large and brilliant fruits cover the branches in autumn and early winter, occasionally finds a place in the gardens of eastern Canada and the northern states.