The Rio Mayo region of northwestern Mexico is a major geographic area whose natural history remains poorly known to outsiders. This new book updates and amends Howard Scott Gentry's Rio Mayo Plants. It reproduces the original text, which appears here with annotations, and contains information on 2,825 taxa - more than twice the number of species first described by Gentry.

The annotated list of plants includes information on distribution, habitat, appearance, common names, and indigenous uses. A new introduction provides historical background and a review of geography and vegetation. It also describes changes to the land and river wrought by agricultural development, expanded grazing, and lumbering.

This updating of his work fills a gap in the botanical literature of this portion of North America and will be useful not only for botanists but also for biogeographers, taxonomists, land managers, and conservationists.