Rheum
(from rheon, an adjective formed from Rha, the old Greek name for Rhubarb. Rheon barbarum has been corrupted into our Rhubarb). Rhubarb. ORD. Polygoneae. About a score species have been referred to this genus, but the number may be reduced; they are hardy, robust, perennial herbs, with thick and slightly woody rhizomes, natives of Siberian, Himalayan, and Eastern Asia. Flowers pedicellate, fasciculate, ebracteolate, the fascicles disposed in narrow, paniculate racemes; perianth of six spreading segments. Leaves large, sinuate-toothed or palmately lobed, three to eight-nerved at base. R. Rhaponticum and its varieties, and R. undulatum, furnish the rhubarb so well-known and extensively employed. Several of the species are very handsome, both in their foliage and in their inflorescence. The rhubarb of commerce, an important medicine, valuable for its mild purgative properties, is afforded by several species of Rheum, of which the following are the principal: 1. R. palmatum, first found wild in 1872-3, by Colonel Prejavalsky, in the Tangut district of Kansu, the extreme north-western province of China; this is the real source of the Russian, or Turkey, Rhubarb. 2. R. officinale, from the Chinese frontier of Eastern Thibet. 3. R. Rhaponticum, generally called English Rhubarb, a native of Southern Siberia, known to have been cultivated, early in the seventeenth century, at Padua, whence it was brought to England, the first plant being raised about the year 1628. It is largely cultivated at Bodicott for medicinal pruposes. A selection of the best-known species is given below. Any of them are well worthy of cultivation as hardy, fine-foliaged plants, for wild gardens, margins of shrubberies, &c. They succeed in almost any soil, but do best where it is rich, and of a good depth. Propagated by seeds, and by division. For culture of the well-known garden varieties, see Rhubarb.
R. acuminatum (taper-pointed). fl. lurid-purple, bloody, or brownish-purple, 1/4in. in diameter, spreading; panicle slightly branched. l. broadly cordate, with a deep sinus, long-acuminate, opaque above, puberulous below; petioles slender, concave above. Root slender, often many feet long. h. 3ft. Sikkim, 1837. (B. M. 4877.) R. australe (Southern). fl. in a long, racemiform, dense panicle; calyx purple. l. sub-orbicular, broadly cordate, obtuse, flat, 3in. to 4in. long, nearly 3in. broad; petoles 4in. long, slender, slightly terete, angulate-sulcate. Stem 6ft. to 10ft. high, leafy. Root fusiform, branched. Nepaul. (S. B. F. G. 269.)
R. Emodi (Emodus). fl. whitish, in a fastigiate, dense panicle. l. broad-ovate, obtuse, cordate, with slightly wavy margins, five to seven-nerved; petioles semi-terete. Stem tall, leafy. h. 6ft. to 10ft. Himalaya.
R. nobile (noble).* fl. green, insignificant, in short, branched panicles; bracts delicate straw-colour, shining, semi-transparent, concave, imbricating, concealing the flowers, the upper ones with pink edges. l., radical ones large, bright glossy green, with red petioles and nerves; stipules pink, fragile. h. upwards of 3ft. Roots thick, fleshy, sometimes many feet long. Sikkim. A lovely species. (G. C. n. s., iii. 91.)
R. officinale (officinal).* fl. greenish, small, collected into dense spikes. l. large, somewhat orbicular-reniform, five-nerved, and cut into five short lobes at the margin; lobes unequally incised. Stem 8ft. to 10ft. high, leafy and much-branched. Thibet, 1871. A stately plant. (B. M. 6135; B. M. Pl. 213; R. H. 1874, 13.)
R. palmatum (palmate-leaved). fl. in a leafy panicle. l. sub-orbicular-cordate, palmately lobed, slightly scarbrous or glabrous above, three to five-nerved; lobes ovate-oblong or lanceolate, acute, undivided, or incised-toothed or pinnatifid; petioles nearly cylindric. h. 5ft. East and North Asia, 1763. (B. M. Pl. 214.) R. Rhaponticum (Rha ponticum-i.e., pontic Rha or Rheum, the name of the drug Rhubarb in the Latin medical writers-applied to the present species by the old botanists). Common cultivated Rhubarb. fl. densely disposed in a leafy, fastigiate panicle. l. sub-orbicular, profoundly cordate, undulated, five-nerved, glabrous above, puberulous below and on the veins; upper ones ovate or acuminate; footstalks long, thick, and fleshy, channeled above, and rounded at the edges. h. 4ft. 1573. (B. M. Pl. 215.)
R. undulatum (undulated). fl. densely disposed in a fastigiate panicle, which is leafy below. l. ovate-cordate, undulated, five to seven-nerved, glabrous above, puberulous beneath; uppermost ones sub-sessile, two or three times longer than broad; petioles semi-terete, loosely channelled above, with rounded margins. Stem 4ft. to 5ft. high, smooth, green. Siberia, &c., 1734. See Fig. 364.