Offers a comprehensive general discussion on the morphology, variability, ability to produce hybrids, evolution, and ecology of the willows along with detailed treatments for about 135 species. Each species entry consists of a thorough review of nomenclature, literature, a description of the habit and habitats of the species, an original map depicting its geographical distribution, a detailed verbal description of its geographical distribution. Species are grouped in 26 sections, each section featuring an identification key to its members.