CACTUS, L. (The old "Cactus" genus can nowadays be almost anything in the Cactaceae family, including Cactus, Pereskia, Opuntia, Melocactus, Echinopsis, Lepismium, Eriosyce, Disocactus, Selenicereus, Cereus, Armatocereus, Pilosocereus, and so on and so on. -Henriette.) Nearly 20 species in the United States. See Opuntia for the Prickly Pears. Almost all have edible fruits, acid and grateful: those of C. bleo are like cherries: those of C. ferox are purple, size of an egg. Many are very troublesome weeds, with formidable thorns.