Cyphostemma is a large genus of flowering plants in the grape family Vitaceae, comprising approximately 250 accepted species. It belongs to the order Vitales and is classified within the class Magnoliopsida. The genus was formally established by Alston in 1931, based on the subgenus Cyphostemma originally described by Planchon, and all its species were formerly accommodated within the broadly defined genus Cissus. Phylogenetically, Cyphostemma is most closely related to Cayratia and Tetrastigma within the Vitaceae.
The genus is notable for its caudiciform growth habit: many species produce a swollen, water-storing stem base (caudex) that allows them to survive extended dry seasons. This adaptation is most pronounced in the succulent species of southern Africa and Madagascar, such as the widely cultivated Cyphostemma juttae of Namibia, which develops a thick, peeling-barked trunk and can grow into a substantial shrub or small tree. Non-succulent species, common across tropical Africa and extending into Arabia and Indochina, are more typical vines with tendrils, lobed leaves, and small grape-like fruits.
The genus is distributed across the tropics and subtropics of the Old World, with its center of diversity in sub-Saharan Africa and Madagascar. The range extends from northeast Africa and southern Arabia eastward through to Indochina. This broad distribution encompasses a range of biomes, from dry savanna and semi-arid scrub to humid tropical forest margins.
Etymology
The genus name Cyphostemma derives from the Greek words kyphos (κυφός), meaning "hump" or "bent," and stemma (στέμμα), meaning "garland" or "wreath." The name alludes to the distinctive swollen, humped stem base characteristic of many species in the genus. The genus was formally circumscribed by Alston in 1931, elevating Planchon's earlier subgenus rank to genus level.
Distribution
Cyphostemma is distributed across the tropics and subtropics of the Old World, with the greatest species richness in sub-Saharan Africa and Madagascar. The range extends from northeast Africa and southern Arabia westward across tropical Africa, and eastward through to Indochina. Succulent, caudex-forming species are concentrated in the arid and semi-arid zones of southern Africa (particularly Namibia and South Africa) and Madagascar.
Taxonomy
All species of Cyphostemma were formerly included in the broadly circumscribed genus Cissus (Vitaceae). Molecular and morphological studies established Cyphostemma as a distinct genus most closely allied to Cayratia and Tetrastigma. The genus was raised to generic rank by Alston in 1931, based on Planchon's subgenus Cyphostemma. Estimates of species number vary among taxonomic databases, ranging from roughly 245 to nearly 300 accepted species.
