The Peterson Identification System shows exactly what features to look for to tell one species from another. The most complete work on the medicinal plants of western North America, this guide offers the best information in the world on the nearly 500 species covered, much of it available for the first time. More than 530 color photographs illustrate the plants. An index to medical topics helps locate information on specific ailments. Symbols next to the plant descriptions provide quick visual warnings for poisonous and allergenic plants. Organized by flower color for fast identification, this guide is an essential aid to apppreciating native plants and the wild areas they inhabit.