POLYGONACEÆ.
RADIX RHEI.
Rhubarb; F. Rhubarbe; G. Rhabarber.
Botanical Origin—No competent observer, as far as we know, has ever ascertained as an eye-witness the species of Rheum which affords the commercial rhubarb. Rheum officinale, from which it seems, at least partly, derived is the only species yielding a rootstock which agrees with the drug.
Rheum officinale Baillon is a perennial noble plant resembling the Common Garden Rhubarb, but of larger size. It differs from the latter in several particulars: the leaves spring from a distinct crown rising some inches above the surface of the ground; they have a subcylindrical petiole, which as well as the veins of the under side of the lamina is covered with a pubescence of short erect hairs. The lamina, the outline of which is orbicular, cordate at the base, is shortly 5-to 7-lobed, with the lobes coarsely and irregularly dentate; it attains 4 to 4½ feet in length and rather more in breadth. The first leaves in spring display before expanding the peculiar metallic red hue of copper.
The plant was discovered in South-eastern Tibet, where it is said to be often cultivated for the sake of its medicinal root; but it is supposed to grow in various parts of Western and North-western China, whence the supplies of rhubarb are derived. It was obtained by the French missionaries about the year 1867 for Dabry, French Consul at Hankow, who transmitted specimens to Dr. Soubeiran of Paris. From one of these which flowered at Montmorency in 1871, a botanical description was drawn up by Baillon.[1801]
To what extent the rhubarb of commerce is derived from this plant is not known. But that the latter may be a true source of the drug is supported by the fact, that there is at least no important discrepancy between it and the accounts and figures, scanty and imperfect though they are, given by Chinese authors and the old Jesuit missionaries; and still more by the agreement in structure which exists between its root and the Asiatic rhubarb of commerce.
We have engaged in 1873 Mr. Rufus Usher at Bodicott ([see below, p. 500]) to cultivate Rheum officinale, which is there admirably succeeding; but it must be granted that as yet the root, notwithstanding the most careful preparation in drying it, is far from displaying the rich yellow of the commercial drug. It is most obviously marked on the other hand with the characteristic ring of stellate markings, which we have constantly observed in many roots of Rheum officinale cultivated by us at Clapham Common near London, as well as at Strassburg or, by other observers, at Paris.
Rheum palmatum L., a species known as long as 1750, has always been supposed to yield also rhubarb, and this has again been asserted by the Russian Colonel Przewalski, who observed in 1872 and 1873 that plant in the Alpine parts of Tangut round the Lake Kuku-nor, in the Chinese province of Kansu, in 36°-38° North Lat.—Rheum palmatum has been frequently cultivated in Russian Asia and in many parts of Europe since the last century, but without producing a root agreeing with Chinese rhubarb. Now, Przewalski states that from this species the drug under notice is largely collected along the river Tetung-gol (or Datung-ho), a tributary of the upper Hoang-ho, northward of the Kuku-nor. Specimens of that root were largely brought to St. Petersburg by Przewalski, but Dragendorff expressly points out in his Jahresbericht for 1877 (p. 78) that it is dissimilar to true rhubarb.
History[1802]—The Chinese appear to have been acquainted with the properties of rhubarb from a period long anterior to the Christian era, for the drug is treated of in the herbal called Pen-king, which is attributed to the Emperor Shen-nung, the father of Chinese agriculture and medicine, who reigned about 2700 b.c. The drug is named there Huang-liang, yellow, excellent, and Ta-huang, the great yellow.[1803] The latter name also occurs in the great Geography of China, where it is stated that rhubarb was a tribute of the province Si-ning-fu, eastward of Lake Kuku-nor,[1804] from about the 7th to the 10th centuries of our era.