The stipe, cap, annulus, veil, gills etc are anatomical features very useful in the identification of the genera and species of mushrooms. Other microscopical and genetic properties are also important in identification. When a fruit-body is very young it is called a primordium . When it develops and its veil opens, it is called a mature, open mushroom. Most white button mushrooms you can find in markets are young, developing examples of closed ones.
Open mushrooms are prone to different kinds of diseases.
Mushrooms, like any living organism, inevitably die and decay after playing an invaluable role in nature. Microscopically, fungi have a filamentous structure. Such filaments are called hyphae . Cells of fungal tissues are thus tubular and are delineated by a chitinous cell wall. Fungal cells may frequently have many nuclei in their cytoplasm.