Often casually called "the Meadow Mushrooms," about 90% of Agaricus species actually reside in forest and other non-grassland habitats. All species exploit the partly decomposed remains of green plants. Some species are edible, even cultivated, while others are toxic. This volume, the result of 40 years of work by R. W. Kerrigan, is a monographic technical resource covering all that is currently known about Agaricus in North America. Authoritative while remaining accessible to the non-specialist, it evaluates Agaricus diversity in terms of living members of natural ecosystems, and as elements of a complex pattern of phylogenetic relationships. Apart from the more technical information, this illustrated volume could also serve as a field guide to the group. Wherever possible, explanations and examples of 'taxonomic' perspectives, practices, and decisions are provided for those readers interested in a deeper understanding of how modern mycology is actually undertaken. Includes keys, descriptions, photographic images, and habitat and use information.