The Flora of North America will be a unique compendium of taxonomic information about the more than 17,000 species of plants that grow in the United States and Canada. This introductory volume presents information on the physical and biological factors that have affected the evolution and distribution of plant life throughout North America. Essays on such topics as geography, paleofloristics, and human impact are written to summarize current knowledge and to provide access to the relevant literature. The almost 100 drawings that accompany the introductory essays were taken from various 19th and 20th century works. They were chosen in part to illustrate plants mentioned within the text and in part as historical examples of the style and quality of botanical illustration from an earlier era to the present. Future volumes of Flora of North America will contain full descriptions of each species, along with information about the species' habitat, geographical range, and basic ecology.