Rheum officinale, Baillon, palmatum, Linne, and var. tanguticum, Maximowicz, and probably other species.

The rhizomes and roots grown in China, Thibet, deprived of most of the bark tissues and carefully dried.

Habitat. W. and C. China, Thibet, Chinese Tartary; mountains, southern exposure - light, loose, sandy and rich black forest soil.

Syn. Turkey or China Rhubarb; Br. Rhei Rhizoma; Fr. Rhubarbe de Chine; Ger. Rhizoma Rhei, Rhabarber.

Rhe'um. L. Rha, the river Volga, upon whose banks it grows and was first found, fr. Gr.

Rheum Rhubarb 266

to now - i. e., it causes purgation.

Ol-fl-ci-na'le. L. officina, workshop; opus, work, + facere, to do - i. e., used in or belonging to the shop or store.

Pal-ma'tum. L. palmatus, fr. palma, palm of the hand - i. e., the much divided leaves.

Tan-gut'i-cum. L. pertaining to Tangut, district of Kansu, in Northwestern China - i. e., plant's habitat.

Rhubarb, contraction of rheubarbarum - rheum + barbarum - i. e., barbarian plant from the Rha (Volga), whence name rha Ponticum - Pontic-rha, R. rhaponti-cum, fr. Pontic or Euxine Sea.

Plants. - Large compact perennial herbs; aerial stem persisting through the winter, after a few years 30 Cm. (1°) high, 10 - 15 Cm. (4-6') thick, branches 25-37.5 Cm. (10-150 long, blunt summit, brown coat from withered scales (ocreas) and leaf-bases; internally fleshy (semi-pulpy) with yellowish juice; leaves very large, petiole .3-5 M.

(12-18') long, 2.5-4 Cm. (1-1 3/5') thick, solid; lamina .6-1.3 M. (2-4°) long and broad, suborbicular, palmately-veined, 5-7-lobed, reticulate, pubescent, pale green; stipules very large; flowering branches (stems) several, 1.5-3 M. (5 - 10°) high, hollow, thick, green, striate, smoothish; flowers May June, 6 Mm. (1/4') long, clusters of 7-10, catkin-like compound panicles, greenish-white; fruit August, small clusters, 12 Mm. (2') long, (6 Mm. (1/4') broad, triangular, wing at each angle, crimson-red; seed solitary. Rhizome, subcylindrical, barrel-shaped, conical, rounds, or plano-convex, flats, or irregular pieces, frequently with a perforation; hard, moderately heavy, 5-17 Cm. (2-7') long, 5-10 Cm.

Fig. 97.   Rheum officinale: n, pistils and stigmas; d, nectar tubes.

Fig. 97. - Rheum officinale: n, pistils and stigmas; d, nectar tubes.

(2-4') thick, or cut into variable shape and size; yellowish-brown, mottled, with alternating, longitudinal striae of grayish-white parenchyma and brownish medullary rays, small stellate groups of fibro-vascular tissue, occasionally reddish-brown cork patches; smooth, sometimes covered with brownish-yellow powder; fracture uneven, granular, characteristic mottled appearance; odor aromatic, characteristic; taste characteristic, slightly bitter, astringent, gritty when chewed, tingeing saliva yellow. Powder, orange-yellow, red with alkalies; microscopically - rosette aggregates of calcium oxalate, many starch grains, .002-.02 Mm. (1/12500-1/1250')broad, few reticulate or spiral tracheal fragments. Tests: 1. Boil .1 Gm. with aqueous solution of potassium hydroxide (1 in 100) 10 Ml. (Cc.), cool, acidulate filtrate with hydrochloric acid, shake with ether 10 Ml. (Cc.); ethereal layer (yellow on standing) shaken with ammonia water 5 Ml. (Cc.) - ammonia water layer cherry-red color (pres. of emodin), ethereal layer remains yellow (pres. of chrysophanic acid); not more than 15 p. c. of the drug should show a hollow or dark central area. Should be kept in tightly-closed containers, adding occasionally a few drops of chloroform or carbon tetrachloride to prevent insect attack. Solvents: alcohol; water. Dose, gr. 5-30 (.3-2 Gm.).

Adulterations. - Irrespective of variety, rhubarb should be moderately heavy, compact, bright color, brittle, broken edges with fresh appearance, red and yellow veins intermingled with white, decidedly aromatic odor, bitter, astringent, slightly gritty, non-mucilaginous, staining saliva yellow; pieces that are porous, mucilaginous taste, dark brown interior should be rejected. Turmeric sometimes added to the powder and also rubbed over unsightly pieces - recognized by its starch grains, as well as by adding to 5 gr. (.3 Gm.) of suspected rhubarb a few drops of chloroform on white paper, when Chinese slightly stains the paper, while the European, or dark-colored Chinese, imparts a deep yellow stain; now on adding a few grains of borax + a drop of hydrochloric acid, if pure rhubarb - stain not changed, if tumeric present - get a distinct red.

Fig. 98.   Russian rhubarb: transverse section.

Fig. 98. - Russian rhubarb: transverse section.

Commercial. - Plants, resembling our garden rhubarb - pie-plant, grow wild and largely under cultivation in Chinese Empire, where a number of species, chiefly the three recognized, furnish the official product. Rhizome, when 8-10 years old, is dug (Tartary, spring, autumn; China, Sept.-Oct.), and, after removing roots and corky layer, is divided into segments (to aid drying), perforated, strung on cords, and suspended in the shade or under cover (house roofs and eaves) to be cured by circulating air, a process that often requires a year and a loss of 80 p. c.; frequently that dried by the sun, heated stones, stoves, ovens, kilns, or brushwood fires, high dried (usually having broad ridges, blackish grooves, heavy disagreeable odor) and the larger roots, tails, are included, both being more or less inferior. Variety and quality are distinguished, in experienced hands, by odor (bouquet), while all kinds are subject to insect attack, which is prevented best by keeping in tightly-closed containers having a tuft of cotton saturated with chloroform or carbon tetrachloride. Most of our supply comes from Hankow, on the Upper Yang-tse, that from Hsining (Tze-chuen and Shensi products) commanding the highest price. There are three varieties: 1, Russian {Turkish, Crown - R. pal-matum), no longer on the market, but consisted of the best rhizome, from Chinese Tartary via Siberia, trimmed to beneath the cambium, perforated with large conical hole (for easy examination), inspected rigorously at Kiachta, refuse burned, the reserve sewed in linen sacks, covered with hide, and sent to Petrograd (St. Petersburg); Turkish ports once supplied it (hence name), being brought from Tartary by caravans through Persia and Anatolia; 2, Chinese (E. Indian - R. officinale, R. palmatum, var. tanguticum, etc.), our official rhizome, having inner bark, and sometimes patches of rough corky layer and twine fibres; color less bright and odor less aromatic than Russian; flourishes best at 2,400-3,000 M. (8,000-10,000°) elevation in the Himalaya and other mountains, on the shady side of damp ravines, with northern exposure; distinguished natively as "northern" and "southern," also as "Shensi"