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Asclepiadaceae A family of erect or twining shrubs or perennial herbs that are sometimes fleshy and usually have white sap. Leaves are opposite or whorled. Inflorescences are cymose. The flowers are regular, and pentamerous, the petals contorted, the stamens often with two pollinia (see POLLINIUM), and the ovary half-inferior. The fruit consists of paired follicles. The seeds are tiny and plumed. There are 348 genera, with about 2900 species, mainly of the tropics and subtropics, especially of S. America.