3. Cynanchum Linn., Sp. Pl. 212. 1753. Gen. Pl. ed. 5.101. 1754; Markgraf in Tutin et al., Fl. Europ. 3:71. 1972.
Woody climbers. Leaves opposite, petiolate. Flowers in axillary or terminal umbelloid cymes. Corolla lobes twisted in bud. Corona double, with 5 inner and 5 outer processes or ± single with appendage on the inner face of each lobe. Pollinia 1 in each cell, pendulous, waxy, without pellucid margin. Follicles fusiform and smooth.
A genus with c. 150 species, distributed in tropical and temperate regions of the world; represented in Pakistan by 6 species.
Hooker, f. (l.c.), Parker (l.c.) and Kitamura (Fl. Afgh. 308. 1960) have treated the genus Cynanchum L. in a broader sense including the genus Vincetoxicum. However, Decaisne (in DC., Prodr. 8: 523. 1844), Boissier (l.c.), Bullock (l.c.) Rechinger, f. (l.c.), Markgraf (l.c.) and Browicz (in Davis, Fl. Turkey 6:167. 1978) have treated Vincetoxicum as a genus distinct from Cynanchum. Accepted in this sense, the genus Cynanchum differs from Vincetoxicum in usually having tubular (sometimes divided) membranous corona with internal processes or scales, whereas Vincetoxicum has simple and deeply divided corona with more or less fleshy or coriaceous segments without internal processes and connate at the base by a membranous structure.