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The saguaro cactus and its cousins the cardon, organ pipe and senita cacti dot the landscape of the Southwestern United States. Indeed, they are the hallmark of this desert landscape. Judging from the shape of the flowers, it is clear, says the author that these cacti originally evolved to accommodate bats as their pollinators. But in order to expand their geographic range into areas where the bats were less abundant, these plants have developed unusual—some might even say bizarre—new mechanisms for attracting pollinators and for reproducing. One species of cactus, for example, is capable of producing four different sexes.