To understand almost any part of the tropical rain forest's fabulously complex web of life, one must first learn to identify a bewildering array of plants. Alwyn Gentry's landmark book, completed just before his tragic death in 1993, is the only field guide to the nearly 250 families of woody plants in the most species-rich region of South America.

As a consummate field researcher, Gentry designed this guide to be not just comprehensive, but also easy to use in rigorous field conditions. Unlike many field guides, which rely for their identifications on flowers and fruits that are only...