324 Materia Mjedica. — Heraclevm gummiferum. part it.

tioles, the margin of the bn.se of which is leafy, ventricose,and sheathing. The umbels are large and many-rayed, com-posed of many-flowered convex umbellules. 1 he involucreis polyphyllous, with the leaflets linear, lanceolate, and deci-duous; as are also the involucels, which, however, are per-sistent. The marginal flowers are hermaphrodite and rayed,the central hermaphrodite without the germen. The marginof the calyx is obsolete. The marginal flowers "have a penta-petalous unequal corolla, the two outer petals being large, di-lated, and somewhat cordate; and the three inner in/lex, cordate,and half the size only of the others. The central flowers arepentapetalous, equal, with inflex cordate petals. The filamentsare five, capillary, with roundish anthers. There is no germenin the central flowers, but in tiie marginal it is oblong, inferior,and crowned with two short styles inserted into a glandularbody, with capitate stigmas. The fruit is' oblong, slightlyemarginate, consisting of two striated seeds, convex on one side,and on the other plane.

Willdenow could not obtain any of the gura-resin from thisplant; but he has no doubt of its being the plant from whichit is obtained. Mr. Jackson, in his account of Marocco, in-forms us, that the ammoniacum plant, which in the Arabic isnamed J'eshook, resembles the fennel', is ten feet in height,and one inch thick in the thickest part of the stem. The plantgrows at El-araiche and M'Sharrah Humellah : and neitherbird nor beast is seen near the spot, but it is attacked by ahorned beetle which perforates the stem with its horn, and thejuice runs out at the wound- The ammoniacum is, however,procured by incisions also, and allowed to drop on the ground,where-it hardens by the air and sun: on which account thatfrom Barbary is mixed with a red earth, and is not saleable inthe London market. The best ammoniacum is brought fromthe East Indies, packed in case.; and chests. It is in large massescomposed of small round fragments or tears : or in separate drytears, which is generally considered a sign of its goodness.

Qualities. — Ammoniacum has a peculiar faint but not un-grateful smell; and a bitter nauseous sweet taste. The tearsare yellow on the outside, and white within; brittle, and breakwith a vitreous fracture. Their specific gravity is 1*207. Am-moniacum is adhesive in the warm hand, softens by heat, butdoes not melt; and is partially soluble in water, alcohol, ethtr,solutions of alkalies, and vinegar. When triturated withwater the solution is milky, but after some time it lets fall aresinous matter; which is the part of the ammoniacum that is

1 Both Dioscorides and Pliny describe ammoniacum as the juice of a species offerula growing in Libya. Dioscor. 1. iii. c. 98. Flin. 1. xii, c. 23.