Mushroom

     Many species of mushrooms seemingly appear overnight, growing or expanding rapidly. This phenomenon is the source of several common expressions in the  English language  including "to mushroom" or "mushrooming" (expanding rapidly in size or scope) and "to pop up like a mushroom" (to appear unexpectedly and quickly). In reality, all species of mushrooms take several days to form primordial mushroom fruit bodies, though they do expand rapidly by the absorption of fluids. [14] [15] [16] [17]      The  cultivated mushroom , as well as the common  field mushroom , initially form a minute  fruiting body , referred to as the pin stage because of their small size. Slightly expanded, they are called buttons, once again because of the relative size and shape. Once such stages are formed, the mushroom can rapidly pull in water from its  mycelium  and expand, mainly by inflating preformed  cells  that took several days ...

     A  mushroom  or  toadstool  is the fleshy,  spore -bearing  fruiting body  of a  fungus , typically produced above ground, on soil, or on its  food  source.  Toadstool  generally denotes one poisonous to humans. [1]      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 ) on the underside of the cap. "Mushroom" also describes a variety of other gilled fungi, with or without stems, therefore the term is used to describe the fleshy fruiting bodies of some  Ascomycota . The gills produce microscopic  spores  which help the fungus spread across the ground or its occupant surface.      Forms deviating from the standard  mor...