The main objective of this book is to provide means for identifying the approximatlely 3438 species of flowering plants, ferns, and fern-allies growing without cultivation in Arizona.

Arizona ranks very high among the States in the richness and diversity of its flora. Approximately 3,200 species of flowering plants and ferns, growing without cultivation, are known to occur within its limits. Many other species have been collected so near the borders of Arizona that they are almost certain to be found in the State. It therefore seems appropriate that the United States Department of Agriculture should undertake publication of a flora of Arizona--Résumé de l'éditeur.