ASCLEPIADACEAE

Texas, or white, milkweed (Asclepias texana) the milkweed family of the flowering-plant order Gentianales, including more than 280 genera and about 2,000 species of tropical herbs or shrubby climbers, rarely shrubs or trees. Most members of the family have milky juice, flowers with five united petals, podlike fruits, and, usually, tufted seeds. The silky-haired seeds are drawn out of their pods by the wind and are carried off. Male and female parts of each flower are united in a single structure. The pollen is massed in bundles called pollinia, pairs of which are linked by a yokelike bar of tissue contributed by the stigma of the pistil. Parts of the pollinia stick to visiting insects, which then carry them to other flowers. In some species the fertility is low, and many-flowered plants often produce few fruits. Common milkweed (Asclepias syriaca) and bloodflower (A. curassavica) often are cultivated as ornamentals. The butterfly-weed (A. tuberosa) of North America has bright orange flowers. Hoya carnosa, which is commonly called wax plant because of its waxy white flowers, is often grown indoors as a pot plant. Succulent plants of the family, such as Hoodia and carrion flower (Stapelia and Huernia), produce offensive odours, attracting flies, which then pollinate the plants. The pitcher plant (Dischidia rafflesiana) has pitcher-shaped leaves that store rainwater. The plant absorbs the water through roots that grow into the pitcher. Ants sometimes drain a pitcher by puncturing the bottom, then fill the cavity with plant materials and use it as a nest for raising young. See also butterfly weed; carrion flower.