Physical description Members of the family are erect or climbing plants, including trees, lianas (woody vines), and herbaceous plants. The leaves are borne oppositely or in spirals and are often palmately lobed or compound. The plants are commonly dioecious, meaning that individuals are either male or female. The flowers are petal-less, and the dry one-seeded fruits are usually achenes or samaras. hemp Hemp (Cannabis sativa). U.S. Fish and Wildlife Service

Major genera and species Cannabis, with 1–3 species, and hops (Humulus), with 3 species, are the most economically important members of the family. The genus Celtis, commonly known as hackberries or nettle trees, contains about 70 species of trees, some of which are grown as ornamentals. The genus Trema, closely related to Celtis, comprises about 40 species of small evergreen trees. Small genera include Aphananthe, Chaetachme, Gironniera, Lozanella, Parasponia, and Pterocletis; the taxonomy of some of these groups is contentious. white stinkwood tree White stinkwood tree (Celtis africana) along the Olifants River in South Africa. © John Lindsay-Smith/Shutterstock.com