A mushroom is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground on soil or on its food source. Like all fungi, mushrooms are not plants and do not undergo photosynthesis. The standard for the name “mushroom” is the cultivated white button mushroom, Agaricus bisporus; hence the word “mushroom” is most often applied to those fungi (Basidiomycota, Agaricomycetes) that have a stem (stipe), a cap (pileus), and gills (lamellae, sing. lamella) or pores on the underside of the cap.