Mammillaria(redirected from Porfiria)
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globular or short-cylindrical cacti. The stem is covered with tubercles that grow from the bases of the leaves. On top of the tubercles are areolae (adapted axillary buds), with tufts of hairs and thorns. The flowers and lateral shoots are borne in the axils of the tubercles. The flowers are usually small and grow in a wreath at the top of the stem. The fruits are berry like and ripen in the second year. There are more than 350 species (according to other sources, only about 200), found in the arid regions of Mexico, Venezuela, and Colombia. They grow on small hills or on mountains with elevations up to 2,800 m above sea level. Some species form large clumps. Many of these cacti are ornamentals; they are raised in greenhouses or as house plants. The plants are propagated from seeds and cuttings.