The largest cactus genus is Opuntia, jointed-stemmed species recognizable by the fleshy stems made up of either cylindrical (in the cane cacti and the chollas) or flattened (in the prickly pears) joints called pads. The large pear-shaped berries of several of these species are edible, e.g., the cultivated varieties of the Indian fig and the tuna. This fruit is common in Mexican markets; the plants have been widely naturalized in the Mediterranean countries, Australia, and elsewhere as a source of food. Most opuntias grow so rapidly to a large and ungainly size that they are unsuitable for cultivation as ornamentals, and in the wild often become weeds.
However, the major economic importance of the cactus family is in the florists' trade. Among those cultivated for their showy blossoms are the Christmas cactus ( Zygocactus ) and species of Echinocereus and of Epiphyllum, the orchid cactus. The pincushion cacti ( Mammillaria ), the golden ball cactus ( Echinocactus ), and the hedgehog cactus ( Echinopsis ) are among the many grown as oddities for their curious appearance.
The nopal ( Nopalea coccinellifera ) is the cactus traditionally cultivated as a host for the cochineal insect, and the hallucinatory drug mescaline occurs in the genera Lophophora (peyote) and Trichocereus. Other cacti are used as a substitute for wood, as stock feed, and for hedges.
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