Agaricus bisporus

(from the article `mushroom`) ...any fleshy fungus fruiting structure. In a very restricted sense, mushroom indicates the common edible fungus of fields and meadows (Agaricus ...
Found on http://www.britannica.com/eb/a-z/a/27

Agaricus bisporus

Agaricus bisporus is an edible basidiomycete mushroom native to grasslands in Europe and North America. It has two color states while immature—white and brown—both of which have various names. When mature, the same mushroom has yet another popular name. When immature and white—this mushroom may be known as common mushroom, button mushroom, w...
Found on http://en.wikipedia.org/wiki/Agaricus_bisporus
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