dogbane, common name for some members of the Apocynaceae, a family of herbs, shrubs, and trees found in most parts of the world but especially in the tropics, where they are often climbing forms. Many species are native to or naturalized in North America. Members of the family are sources of such economically important products as drugs and tannins. The vincristine alkaloids that are so effective in the treatment of Hodgkin's disease were discovered in the Madagascar periwinkle, Catharanthus roseus. Quebracho is obtained from Aspidosperma quebracho blanco, the white quebracho; latex for rubber was extracted from some tropical genera, e.g., Landolphia; and fiber, e.g., Indian hemp, is retted from north temperate species of Apocynum, the dogbane genus (not to be confused with the Indian hemp plant, Cannabis ). Some dogbanes are ornamentals, e.g., the shrubby oleanders, or rosebays (genus Nerium ), the yellow oleander ( Thevetia neriifolia ), and the small blue-flowered periwinkles, or running myrtle (chiefly Vinca minor ), all of which are evergreen plants native to the Old World. The dogbane family is closely related and similar to the milkweed family; both have a characteristic milky sap. Some dogbanes are poisonous, e.g., the oleanders and the ordeal tree ( Tanghinia venenifera ) of Madagascar. Dogbane is classified in the division Magnoliophyta, class Magnoliopsida, order Gentianales.