Cayratia is a genus of flowering plants in the grape family Vitaceae (order Vitales), comprising about 60 species of mostly woody lianas found across tropical and subtropical regions of Asia, Africa, Australia, and the Pacific islands. The genus belongs to tribe Cayratieae and is most closely related to Tetrastigma and Cyphostemma.
Plants are hermaphroditic or polygamo-monoecious vines with tendrils that are typically 2- or 3-furcate. Leaves are compound, either 3-foliolate or pedately 5-foliolate. Inflorescences are compound dichasia or corymbose polychasia, bearing small 4-merous flowers with four spreading petals that fall separately, four stamens, and a well-developed 4-lobed or undulately lobed disk. The style is short with a slightly expanded stigma. Fruits are globose berries containing 1-4 seeds; the seeds are semiglobose with a semicircular or T-shaped endosperm cross-section.
The genus was described by Jussieu in 1818 (Dict. Sci. Nat. 10: 103). Recent phylogenetic work found the traditional circumscription to be non-monophyletic, resulting in the transfer of species such as Cayratia japonica to the genus Causonis. The type species is Cayratia pedata. Flora of China recognizes two subgenera: subg. Cayratia and subg. Discypharia, distinguished by inflorescence articulation and seed morphology.
Distribution
Cayratia species are distributed across tropical and subtropical regions of Asia, Africa, Australia, and islands of the Pacific Ocean. Of the approximately 60 species worldwide, 17 occur in China (nine of which are endemic), with the remainder spread across Africa, tropical Asia, and Oceania.
Taxonomy
The genus Cayratia was described by Antoine Laurent de Jussieu in 1818 (Dict. Sci. Nat. 10: 103). Within Vitaceae, it belongs to tribe Cayratieae and is most closely related to Tetrastigma and Cyphostemma. Phylogenetic studies revealed that the traditional circumscription was non-monophyletic; notably, Cayratia japonica has been transferred to the genus Causonis. The type species is Cayratia pedata. Flora of China recognizes two subgenera: subg. Cayratia (inflorescence axis articulate with bracts; seeds semiglobose with a smooth abaxial surface) and subg. Discypharia (inflorescence axis not articulate, without bracts; seeds obovoid-elliptic with a raised ventral mid-raphe).
