Designed as a successor to the classic volume by Hitchcock and Chase, this book reflects current taxonomic thought and includes keys, illustrations, and distribution maps for the nearly 900 native and 400 introduced species that have been found in North America north of Mexico.
In addition, it presents keys and illustrations for several species that are known only in cultivation or are of major agricultural significance, either as progenitors of bread wheat and corn or as a major threat to North American agriculture because of their ability to hybridize with crop species.