type of basidium fungus characterized by spore-bearing gills on the underside of the umbrella- or cone-shaped cap. The name toadstool is popularly reserved for inedible or poisonous mushrooms, but this classification has no scientific basis. The only safe way of distinguishing between the edible and the poisonous species is to learn to identify them. Some poisonous mushrooms are of the genus Amanita. The genus includes the fly agaric, Amanita muscaria, and the death angel or destroying angel, A. virosa.
The use of edible mushrooms for food dates back at least to early Roman times. Originally a delicacy for the elite, mushrooms are now extensively grown on a commercial scale, especially the cultivated mushroom or champignon, Agaricus bisporus, and the shiitake mushroom, Lentinus edodes. Their culture requires careful control of temperature and humidity. The bulk of the crop in the United States is grown near Philadelphia. In Europe more than 50 species of mushrooms are marketed. Although mushrooms contain some protein and minerals, they are largely composed of water and hence are of limited nutritive value.
The truffle, puffball, and other edible fungi are sometimes also called mushrooms. In all cases the term mushroom is properly restricted to the above-ground portion, which is the reproductive organ. Mushrooms are classified in the kingdom Fungi, phylum (division) Basidiomycota.