Psathyrella
Psathyrella is a large genus of about 400 species, and is similar to the genera "Coprinellus", "Coprinopsis", "Coprinus" and "Panaeolus", usually with a thin cap and white or yellowish white hollow stem. The caps do not self digest as do those of "Coprinellus" and "Coprinopsis". Some also have brown spores rather than black. These fungi are often drab-colored, difficult to identify, and all members are considered inedible or worthless (for eating) and so they are often overlooked. However they are quite common and can occur at times when there are few other mushrooms to be seen. The first  report of a gilled mushroom fruiting underwater is "Psathyrella aquatica". The genus name "Psathyrella" is a diminutive form of "Psathyra", derived from the Greek word ψαθυρος, "psathuros" 'friable'. The type species of "Psathyrella" is "Psathyrella gracilis", which is now known as "Psathyrella corrugis". Characteristics. In order to identify the species it may be necessary to take into account the presence and nature of any veil remnants on cap (which may only be visible on very young fruiting bodies), the colour of young fruiting bodies, which is often more vivid than with older ones, whether the cap is hygrophanous (it can  well be a translucent brown or ochre colour in a humid state but a pure opaque white on drying out), and the spore size and the presence and nature of cheilocystidia, pleurocystidia and caulocystidia, distinctive sterile cells on the gill face, gill edge and stipe respectively. All Psathyrella species are unusually fragile, and both the cap and stem break with very little effort. Unlike most agarics, the caps of "Psathyrella species" easily break into triangular shaped pieces. Selected species. "For complete list see" List of "Psathyrella" species