genus of ornamental and drug plants in the dogbane family (Apocynaceae), with more than 40 species of woody vines, shrubs, or small trees that are native to tropical Africa and Southeast Asia. The flower petals of some species are drawn out into long threads. The bark and seeds of some vinelike species contain toxic alkaloids called strophanthins, which are used as arrow poisons and in low dosages as cardiac and vascular stimulants. One species, S. sarmentosus, is a source of the drug cortisone.