No Plants say "desert" quite like cacti. Their prickly nature aside, cacti and the desert habitats in which they reside are especially fragile. Indeed, Saguaro National Park and Organ Pipe Cactus National Monument were established primarily to protect the largest concentrations of these respective species. Others, such as the Pima pineapple cactus, are less conspicuous but also more rare and in need of special protection and conservation.<P>In Cacti of the Desert Southwest, botanist Meg Quinn describes eighty of the most significant cacti found in the Sonoran, Chihuahuan, and Mojave deserts. For ease of identification, all are depicted in color photographs and nearly all are shown in full flower.