( 599 ) XXXIII. On the Plant which yields the Gum Ammoniacum. By Mr. David Don, Libr. L.S. Read December 7, 1830. To discriminate and characterize those plants which more immediately administer to the wants and comforts of man, is one of the chief objects of practical botany ; but it is a task replete with difficulties, — the countries whence many of the substances are derived, particularly those belonging to the Ma-teria Medica, being generally remote and often inaccessible to travellers. Although the gum Ammoniacum has held a place in the Ma-teria Medica from a very early period, yet the plant from which it is obtained has hitherto remained almost totally unknown ; and the same may be said of the analogous gum Galbanum, and many other articles derived from the vegetable kingdom enumerated in the Pharmacopoeia. It is true, Dioscorides and Pliny mention the plant which yields the gum Ammoniacum, the former under the appellation of Agasyllis, and the latter under that of Metopium, and give Libya as its native country : but if the gum was anciently imported thence, it must have been the produce of a different plant from the one I shall shortly describe ; and probably identical with the species of Ferula represented by Jackson in his Account of Morocco, as the gum now comes to Europe by way of the Levant and India. Dioscorides, whose opinion is adopted by all subse-VOL. XVI, 4 II quent
BioStor
