2 Spec. Plant. Willd. ii. 488. Cl 9. Ord. 3. Enneandria Trigynia. Nat. ord. Polygonaceae. G. 803. Calyx none. Corolla six-cleft, persistent. Seed one. Sp. 2. R. undulatum. Waved-leaved Rhubarb. Amoen. Acad. iii.

212, t.4. Sp. 3. R. palniatum. Palmatum Rhubarb. Med. Bot. Sd edit.

662. t.231. Phil. Trans, iv. 292. t. 12, 13.

1 The pigment called sap green is the inspissated juice of this berry, with the addition of an alkali.

Dioscoridis. The rhubarb of the Greeks was the root of Rheum Rhaponticum.

1. Rheum undulatum.

Officinal. Rheum undulatum; radix, Dub. The root of Waved-leaved Rhubarb.

This species of rheum was supposed by Boerhaave to be the true Chinese rhubarb; and, as it is not unlikely that foreign rhubarb is taken from several species, that which we receive by way of Canton, which certainly differs, more than simply in the drying, from that which comes through Russia, may be the produce of this plant: on this account the Dublin College has given it a place in the list of materia medica.1 It is a native of China and Siberia, but grows well in this-country. The root divides into a number of thick fibres, which run deep, and are extremely yellow within; the leaves, which appear early in the spring, are supported on moderately thick footstalks, channelled on their under side, and plain on their upper: the leaves are long, running to a point, much waved on their edges, a little hairy on the upper surface, and very strongly veined on the under: the flower-stem is of a pale brownish colour, rising about four feet high, and dividing into several loose panicles, or bunches of white flowers, which appear in May, and are succeeded by triangular seeds that ripen early in the season.

2. Rheum palmatum.

Officinal. Rheum, Lond. Rhei radix, Edin. Dub. Rhubarb root.

Syn. Aechte Rhabarber (G., Dutch, Dan., Swed.), Ruibarbo (S., Port), Haihoung, or E-Tah-ro-ang (Chinese), Daiwoo (Japanese), Variatoo Kalung (Tarn.), Ruwend (Arab.), Reywand (Pers.), Rewund Chini (Duk.).

This species, like the former, is a native of China and Tar-tary: it is said to grow on the snowy mountains of Boutan and of Dauria, and arrives at considerable perfection when cultivated in this country. The root is perennial, thick, oval, branched, externally brown, and internally of a deep yellow colour: the stern, which rises eight or ten feet in height, is erect, round, hollow, jointed, very slightly furrowed, and maculated with small, oblong, purple streaks : the lower leaves stand upon long smooth petioles2; are numerous, large, divided into five segments, which are deeply sinuated, toothed, and strongly ribbed, the petiole being divided at its apex into the five midribs of the segments; of a deep green colour, rough above, and pale and villous below: those of the stem spring from the joints, are also petiolate, and gradually lessen in size towards the top of the stem; there is a sheathing stipule or ochrea at the base of each stem-leaf. The flowers spring from the axilla of the base in numerous panicled clusters: they appear in May: the corolla is divided into six obtuse segments, of a greenish white colour, tinted with light pinkish purple : the filaments are nine, slender, the length of the corolla, and furnished with oblong double anthers: the style is short, with three reflected capitate stigmas; and the germen is a triangular seed, enclosed in a capsule with three membranous reddish margins or alae.

1 Some seeds given by a dealer in rhubarb to Kauw Boerhaave yielded plants both of the R. undulatum and R. palmatum.

2 These make a much better tart than the leaf-stalks of R. undulatum, the species generally employed by the pastrycook.

This plant has been generally believed to be the species which yields the foreign rhubarb; and, under this belief, a very excellent and correct description of it was given by Dr. Hope, Professor of Botany at Edinburgh, in the Philosophical Transactions for 1765. He had raised it from seed sent to him by Dr. Mounsey from Petersburgh two years before, and found that the root possessed all the medicinal qualities of the best foreign rhubarb. Since that period, many laudable attempts have been made to introduce the cultivation of rhubarb into this country, in sufficient quantity to supply our domestic consumption of this valuable drug : but although many individuals have reared large quantities, and some of it has been extremely good, yet so powerful is prejudice, that very little of it can be sold, and the efforts, therefore, of the cultivators have of late very much relaxed.2 It is still, however, uncertain which of the species of rheum yields the foreign rhubarb; nor is it of very great importance, as the roots of the two species above described, and of another, the R. Australe or Enodi, accord so very closely in their medicinal powers, that any of them may be used with equal certainty of success.3 The R. compaction accords with the accounts given by the Bucharians of the plant and the form of the leaf, which, according to Sievers, they describe as round, dentated on the margin, with almost spinous processes, but it has a white root.

The R. Rhaponticum, which is supposed to be the rhubarb of the ancients, yields good rhubarb.

1 Qy. Whether is the floral envelope calyx or corolla?-It is white at first, becomes red and succulent, and is persistent.

2 For an excellent account of those different trials, and some very judicious observations on the mode of cultivating rhubarb, see Miller's Dictionary, edited by Dr. Martyn, article Rheum.

3 The latest account of rhubarb is given by my friend and late pupil, Mr. Royle, in the Calcutta Medical Transactions for 1827. He says one species, R. enodi of Wallich, is found in great abundance on the Chur mountain, at an elevation of 9,000 feet. He adds, "the table land of Tartary is covered with Rhubarb at the height of 16,000 feet; and there is abundance at Ludak, in lat. 37°, whence some of very fine quality was sent to Captain Kennedy by Mr. Moor-croft."- Trans, of the Med. and Phys. Soc. of Calcutta, vol. iii. p, 440. Mr. Royle, who is now (1833) in England, does not think that R. enodi yields the officinal rhubarb.