Trees or shrubs. Leaves opposite, often coarsely serrate, usually gland-dotted and aromatic; stipules absent. Flowers bisexual or unisexual, solitary or in racemes, cymes or panicles. Receptacle cup shaped. Perianth segments 4 or more in 2 or 3 rows. Stamens indefinite in number or a multiple of the perianth segments, perigynous; filaments with 2 appendages; anthers sessile or nearly so opening by basal valve. Carpels several or many, free, superior. Fruits several to many plumose nuts enclosed in the enlarged floral tube. 6–7 gen., trop. and subtrop.