Characters.—Flowers unisexual, amentaceous. Stamens distinct or monadelphons; anthers 2-celled. Ovary superior, 1-celled; ovules numerous, erect, at the base of the cell, or adhering to the lower part of the sides; style 1 or 0, stigmas 2 or 4. Fruit coriaceous, 1-celled, 2 valved, many-seeded. Seeds either adhering to the lower part of the axis of each valve, or to the base of the cell; comose; albumen 0; embryo erect; radicle inferior.—Trees or shrubs. Leaves alternate, simple, with deliquescent primary veins, and frequently with glands; stipules deciduous or persistent (Lindley).
Properties.—The barks of the species of this order are astringent and tonic; the astringency being due to tannic acid, the tonic property to salicine or some other bitter principle. An oleo-resinous or balsamic substance, of a stimulant nature, is secreted by the buds of some of the species.