1	"Leafless or the leaves reduced and scale-like; corona double"	2
1	"Leafy shrubs, erect or twining; corona simple"	3
2	"Pollen masses pendulous; stems cylindrical"	Sarcostemma
2	"Pollen masses erect or horizontal; stems 4-angled, fleshy"	Stapelia
3	"Plant erect"	Asclepias
3	"Plant twining, climbers"	4
4	"Leaves linear"	5
4	"Leaves lanceolate, ovate or deltoid"	6
5	"Pollen masses pendulous; corolla almost rotate"	Rhyncharrhena
5	"Pollen masses erect; corolla campanulate"	Leichhardtia
6	"Corolla tube c. 12 mm long"	Araujia
6	"Corolla tube c. 2 mm long"	Cynanchum