The fungi shown above is a fruit-body arising from the mycelium . The basal part of its stipe , which is still carrying remnants of the mycelium and casing, will be cut and discarded. Of course, our interests will be immediately focused on the internal structure of this macroscopic Basidiomycete fungus. One of the usual methods to appreciate such structures is to bisect the fruit -body from its central point through the cap and stipe. In technical terms this is a vertical median section that provides us with two symmetrical halves.
Gills produce the basidiospores of A. bisporus .
The surface covering of the gills is called the hymenium . It consists of a row of specialized cells called basidia . These cells are determinants of the large group of fungi classified as Basidiomycota . Beneath the gills there is a cavity, the hymenial chamber, which is still closed in this illustrated sample. When a fungus matures, this cavity opens and basidiospores are shed to germinate into new mycelia.