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(milkweed), a family of dicotyledonous plants. They are creeping, climbing, or erect shrubs or subshrubs and herbs; these plants are rarely trees. The leaves are generally opposite, entire, and exstipulate. The flowers are bisexual, usually regular, and five-petaled. The corolla is sympetalous and often has a crown. The stamens and the gynoecium form a gynostegium. The pollen grains are in pollinia; more rarely they are in tetrads. The distinctive structure of the flower is adapted to cross-pollination by insects. The fruit has two follicles, which are somewhat fork-shaped and resemble a swallow’s tail. The seeds usually have a pappus of silky fibers. Plants of the family Asclepiadaceae are characterized by the presence of a milky juice (often poisonous) and intraxylary phloem (bast).
There are approximately 290 genera (2,000 species), distributed primarily in tropical regions; some species are also encountered in subtropical and temperate regions. Eight or nine genera, comprising approximately 40 species, are found in the USSR. The most important genera include Asclepias (milkweed), Vinatoxicum, and Periploca. There are many poisonous, medicinal, and ornamental plants in this family (condurango, wax plant, and stapelia); some species yield dye substances and fiber (species of Marsdenia and Calotropis).