AGARICUS (derived from Agaria, the name of a town in Sarmentosa). Mushroom. ORD. Fungi. The most extensive genus known. It, however, contains but one or two species of cultural value. The most important ones are the common field mushroom, AGARICUS campestris (Fig. 44), the Fairy Ring mushroom, AGARICUS pratensis, and AGARICUS vaginatus. Familiar species are the Parasol mushroom, AGARICUS procerus St. George's mushroom, AGARICUS gambosus and the deadly Fly Agaric, AGARICUS muscarius For practical purposes the majority of this genus are poisonous, and many virulently so. Great care must be exercised in experimenting with unknown species, even by experienced fungologists. See Mushroom.