The Natural History of Pliny, Volume 3 (of 6)

It is universally agreed, that the best gum is that produced from the Egyptian thorn;860 it is of variegated appearance, of azure colour, clean, free from all admixture of bark, and adheres to the teeth; the price at which it sells is three denarii per pound. That produced from the bitter almond-tree and the cherry861 is of an inferior kind, and that which is gathered from the plum-tree is the worst of all. The vine, too, produces a gum,862 which is of the greatest utility in healing the sores of children; while that which is sometimes found on the olive-tree863 is used for the tooth-ache. Gum is also found on the elm864 upon Mount Corycus in Cilicia, and upon the juniper,865 but it is good for nothing; indeed, the gum of the elm found there is apt to breed gnats. From the sarcocolla866 also—such is the name of a certain tree—a gum exudes that is remarkably useful to painters867 and medical men; it is similar to incense dust in appearance, and for those purposes the white kind is preferable to the red. The price of it is the same as that mentioned above.868