Agaricus

Agaricus is a genus of mushrooms containing both edible and poisonous species, with over 400 members worldwide and possibly again as many disputed or newly-discovered species. The genus includes the common ("button") mushroom (Agaricus bisporus) and the field mushroom (A. campestris), the dominant cultivated mushrooms of the West. Members of Agaricus are characterized by having a fleshy cap or pileus, from the underside of which grow a number of radiating plates or gills, on which are produced the naked spores. They are distinguished from other members of their family, Agaricaceae, by their chocolate-brown spores. Members of Agaricus also have a stem or stipe, which elevates it above the object on which the mushroom grows, or substrate, and a partial veil, which protects the developing gills and later forms a ring or annulus on the stalk. The genus contains the most widely consumed and best-known mushroom today, A. bisporus, with A. arvensis, A. campestris and A. subrufescens also being well-known and highly regarded. A. porphyrocephalus is a choice edible when young, and many others are edible as well, namely members of sections Agaricus, Arvense, Duploannulatae and Sanguinolenti. A notable group of poisonous Agaricus is the clade around the yellow-staining mushroom, A. xanthodermus. One species reported from Africa, A. aurantioviolaceus, is reportedly deadly poisonous. Far more dangerous is the fact that Agaricus, when still young and most valuable for eating, are easily confused with several deadly species of Amanita (in particular the species collectively called "destroying angels", as well as the white form of the appropriately-named "death cap" Amanita phalloides), as well as some other highly poisonous fungi. An easy way to recognize Amanita is the gills, which remain whitish at all times in that genus. In Agaricus, by contrast, the gills are only initially white, turning dull pink as they mature, and eventually the typical chocolate-brown as the spores are released.