Climbing or erect, glabrous or pubescent, softly woody plants usually with bisexual flowers, rarely dioecious. Leaf-like structures (cladodes) solitary or fascicled, flat, angled or terete, arising in the axils of cauline leaves but sometimes absent from flower-bearing branchlets. Leaves cauline, alternate, scale-like, usually brown and at least partially scarious, often with a spine from the abaxial surface; Ovary superior, ± sessile, 3-celled; Fruit usually a red 1- to few-seeded berry; Seeds globose or partly angled.
Africa present, Asia present, Asia-Tropical, Australasia, Europe present, Madagascar present, Old World present
Widespread in Europe, Africa, Madagascar, and Asia; in Malesia 2 spp., one of which is widespread in the Old World and the single one known from Australia. There are probably fewer than 100 spp., but the taxonomy of the genus is poorly understood.
The morphology of the spines has been discussed by Cusset & Tran (). The nature of the leaf-like organs (cladodes) is controversial. They are most frequently treated as axillary structures, i.e. modified branches (e.g. ), and my own work confirms this. However, Arber () believed that in a few species they were in fact leaves, while Schlittler () concluded that they are leaves in all species.
Back. & Bakh.f. - in Fl. Java. 1968: 92
Hutch. - in Fam. Fl. Pl., ed. 2. 1959: 608
Linne, Gen. Pl., ed. 5. 1754: 147
Krause - in E. & P., Nat. Pfl. Fam., ed. 2, 15a. 1930: 362
Baker - in Fl. Trop. Afr. 1898: 425
Baker - in J. Linn. Soc. Bot. 1875: 594
Bth. - in Fl. Austr. 1878: 17
Jessop - in Bothalia. 1966: 31