4. RHAMNUS L.
Trees or shrubs, with terete often spinescent branches, without a terminal bud, scaly or naked axillary buds and acrid bitter bark. Leaves alternate or rarely obliquely opposite, conduplicate in the bud, petiolate, feather-veined, entire or dentate, stipulate. Flowers perfect or polygamo-diœcious, in axillary simple or compound racemes or fascicled cymes; calyx campanulate, 4—5-lobed, the lobes triangular-ovate, erect or spreading, keeled on the inner surface, deciduous; disk thin below, more or less thickened above; petals 5, inserted on the margin of the disk, ovate, unguiculate, emarginate, infolded round the stamens, deciduous, or 0; stamens 4 or 5; filaments very short; anthers oblong-ovoid or sagittate, rudimentary and sterile in the pistillate flower; ovary free, ovoid, included in the tube of the calyx, 2—4-celled, rudimentary in the staminate flower; styles united below, with spreading stigmatic lobes or terminating in a 2—3-lobed obtuse stigma; ovule erect from the base of the cell. Fruit drupaceous, oblong or spherical; flesh thick and succulent, inclosing 2—4 separable cartilaginous 1-seeded nutlets. Seeds erect, obovoid, grooved longitudinally on the back, with a cartilaginous seed-coat, the raphe in the groove, or convex on the back, with a membranaceous seed-coat, the raphe lateral next to one margin of the cotyledons; embryo large, surrounded by thin fleshy albumen; cotyledons oval, foliaceous, with revolute margins, or flat and fleshy.
Rhamnus with about sixty species is widely distributed in nearly all the temperate and in many of the tropical parts of the world with the exception of Australasia and the islands of the Pacific Ocean. Of the five species indigenous to the United States three attain the size of small trees. The fruit and bark of Rhamnus are drastic, and yield yellow and green dyes. The European Rhamnus cathartica L., the Buckthorn, has long been used as a hedge plant in northern Europe, and in eastern North America, where it has now become sparingly naturalized.
The generic name is from ῥάμνος, the classical name of the Buckthorn.
CONSPECTUS OF THE NORTH AMERICAN ARBORESCENT SPECIES.
Flowers polygamo-diœcious, in sessile umbels; calyx 4-lobed; petals 0; anthers oblong-ovoid; lobes of the stigma elongated, spreading; fruit red; seed grooved on the back; seed-coat cartilaginous; leaves often sharply toothed, persistent; winter-buds scaly.1. [R. crocea] (G). Flowers perfect, in pedunculate umbels; calyx 5-lobed; petals 5; anthers sagittate; lobes of the stigma short and obtuse; fruit black; seed rounded on the back; seed-coat membranaceous; leaves deciduous; winter-buds naked. Peduncles shorter than the petioles.2. [R. caroliniana] (C). Peduncles longer than the petioles.3. [R. Purshiana] (B, G).
1. [Rhamnus crocea] Nutt.
Leaves persistent, often in fascicles, elliptic, broad-ovate to suborbicular, rounded and often apiculate at apex, glandular-denticulate with minute teeth, coriaceous, yellow-green and lustrous on the upper surface, pale and frequently bronzed or copper color on the lower surface, glabrous or often puberulous while young, with a prominent midrib and slender primary veins, ¼′—¾′ long; petioles short and stout; stipules minute, acuminate. Flowers polygamo-diœcious, on slender often puberulous pedicels, in small clusters from the axils of the leaves or of small lanceolate persistent bracts on shoots of the year; calyx 4-lobed, with acuminate lobes, about ⅛′ long; petals 0; stamens rather shorter than the calyx, with short stout incurved filaments and large ovoid anthers, minute and rudimentary in the pistillate flower; ovary ovoid, contracted into a long slender style divided above the middle into two wide-spreading acuminate stigmatic lobes, rudimentary in the staminate flower. Fruit red, obovoid, slightly grooved or lobed at maturity, ¼′ long, with thin dry flesh and 1—3 nutlets; seed broad-ovoid, pointed at apex, deeply grooved on the back and ⅛′ long, with a thin membranaceous pale chestnut-colored coat.
A shrub, 6′—3° high, with slender rigid often spinescent branchlets forming thickets.
Distribution. Coast mountains of central and southern California. Passing into
Rhamnus crocea var. ilicifolia Greene.
Leaves oval or orbicular, spinulose-dentate, often golden beneath and 1′—1½′ long and ¾′—1′ wide. Flowers with 4 or occasionally 5 calyx-lobes and stamens.
A tree, occasionally 25° high, with a trunk 6′—8′ in diameter, stout spreading branches, and slender branchlets yellow-green and puberulous or glabrate when they first appear, becoming dark red or reddish brown and glabrous in their second season. Winter-buds obtuse, barely more than 1/16′ long, with small puberulous apiculate imbricated scales ciliate on the margins. Bark of the trunk usually from 1/16′—⅛′ thick, the dark gray surface slightly roughened by minute tubercles.
Distribution. California, valley of the Sacramento River southward along the western slopes of the Sierra Nevada, and on the coast ranges and southern mountains to San Diego County; Arizona, Oak Creek and Sycamore Cañons, near Flagstaff, Coconino County, (P. Lowell), Copper Cañon, west of Camp Verde, Yavapai County, and on the Pinal and Santa Catalina Mountains.
Passing into
Rhamnus crocea var. insularis Sarg.
A form with larger less prominently toothed leaves sometimes 3′ long and 1½′ wide, rather larger flowers, with shorter and broader calyx-lobes a less deeply divided style, and larger fruits. A tree often growing to the height of 25°—30°, flowering later than the var. ilicifolia, and not uncommon on the islands of the Santa Barbara group and on the mountains of the adjacent mainland. A form (f. pilosa Trel.) with narrow revolute leaves densely pilose throughout, occurs in the Santa Maria valley of the mountains near San Diego.
2. [Rhamnus caroliniana] Walt. Indian Cherry.
Leaves deciduous, elliptic-oblong or broad-elliptic, acute or acuminate, cuneate or somewhat rounded at base, remotely and obscurely serrate, or crenulate, densely coated when they unfold with rusty brown tomentum, and at maturity thin, dark yellow-green above, paler below, glabrous or somewhat hairy on the lower surface, 2′—6′ long and 1′ to nearly 2′ wide, with a prominent yellow midrib and about 6 pairs of conspicuous yellow primary veins; turning yellow in the autumn before falling; petioles slender, pubescent, ½′ to nearly 1′ in length; stipules nearly triangular. Flowers appearing from April to June when the leaves are almost fully grown, on slender pedicels about ¼′ long, in few-flowered pubescent umbels, on peduncles varying from ⅛′—½′ in length; calyx 5-lobed, with a narrow turbinate tube and triangular lobes; petals 5, broad-ovate, deeply notched at apex and folded round the short stamens; ovary contracted into a long columnar style terminating in a slightly 3-lobed stigma. Fruit ripening in September and sometimes remaining on the branches until the beginning of winter, globose, ⅓′ in diameter, black, with thin sweet rather dry flesh and 2—4 nutlets; seeds obtuse at apex, rounded on the back, reddish brown, about ⅕′ long.
A tree, 30°—40° high, with a trunk 6′—8′ in diameter, small spreading unarmed branches, and slender branchlets light red-brown and puberulent or covered with a glaucous bloom when they first appear, becoming slightly angled, gray, and glabrous, and marked during their second season by the small horizontal oval leaf-scars; more often a tall shrub, with numerous stems 15°—20° high. Winter-buds naked, hoary-tomentose. Bark of the trunk about ⅛′ thick, slightly furrowed, ashy gray and often marked by large black blotches. Wood rather hard, light, close-grained, not strong, light brown, with lighter colored sapwood of 5 or 6 layers of annual growth.
Distribution. Borders of streams on rich bottom-lands, and on limestone ridges; Virginia to western Florida and westward through the valley of the Ohio River to southern Iowa and southeastern Nebraska, eastern Kansas, the valley of the Washita River, Oklahoma (Ardman County), and to Kendall, Kerr and Uvalde Counties, western Texas; occasionally tree-like in western Florida and Mississippi, and of its largest size only in southern Arkansas and the adjacent portions of Texas; very abundant on the limestone barrens of central Kentucky and Tennessee.
3. [Rhamnus Purshiana] DC. Bearberry. Coffee-tree.
Leaves deciduous, broad-elliptic, obtuse or bluntly pointed at apex, rounded or slightly cordate at base, finely serrate, or often nearly entire, with undulate margins, thin, villose with short hairs on the lower surface and on the veins above, 1½′—7′ long, 1½′—2′ wide, conspicuously netted-veined, with a broad and prominent midrib and primary veins; turning pale yellow late in the autumn before falling; petioles stout, often pubescent, ½′—1′ in length; stipules membranaceous, acuminate. Flowers on slender pubescent pedicels ¼′—1′ long, in axillary cymes on slender pubescent peduncles ½′—1′ in length on shoots of the year; calyx nearly campanulate, with 5 spreading acuminate lobes; petals 5, minute, ovate, deeply notched at apex, and folded round the short stamens; stigma 2 or 3-lobed. Fruit globose or broad-obovoid, black, ⅓′—½′ in diameter, slightly or not at all lobed, with thin rather juicy flesh, and 2 or 3 obovoid nutlets usually ⅓′ long, rounded on the back, flattened on the inner surface, with 2 bony tooth-like enlargements at base, 1 on each side of the large scar of the hilum, and a thin gray or pale yellow-green shell; seeds obtuse at apex, rounded on the back, seed-coat thin and papery, yellow-brown on the outer surface, bright orange color on the inner surface like the cotyledons.
A tree, 35°—40° high, with a slender trunk often 18′—20′ in diameter, separating 10°—15° from the ground into numerous stout upright or sometimes nearly horizontal branches, and slender branchlets coated at first with fine soft pubescence, pale yellow-green or reddish brown, and pubescent, glabrous, or covered with scattered hairs in their second season and then marked by the elevated oval horizontal leaf-scars; often shrubby and occasionally prostrate. Winter-buds naked, hoary-tomentose. Bark of the trunk rarely more than ¼′ thick, dark brown to light brown or gray tinged with red, broken on the surface into short thin scales. Wood light, soft, not strong, brown tinged with red, with thin lighter colored sapwood. The bark possesses the drastic properties peculiar to that of other species of the genus, and is a popular domestic remedy in Oregon and California, and under the name of Cascara Sagrada has been admitted into the American materia medica.
Distribution. Rich bottom-lands and the sides of cañons, usually in coniferous forests; shores of Puget Sound eastward along the mountain ranges of northern Washington to the Bitter Root Mountains of Idaho and the shores of Flat Head Lake, Montana, and southward to central California; Arizona, southern slope of the Grand Cañon of the Colorado River, Coconino County (A. Rehder), Cave Creek Cañon, Chiricahua Mountains, Cochise County (J. W. Toumey).
Occasionally cultivated in the gardens of western Europe and of the eastern United States.