Mycena

Mycena is a large genus of small saprotrophic mushrooms that are rarely more than a few centimeters in width. They are characterized by a white spore print, a small conical or bell-shaped cap, and a thin fragile stem. Most are gray or brown, but a few species have brighter colors. Most have a translucent and striate cap, which rarely has an incurved margin. The gills are attached and usually have cystidia. Some species, like "Mycena haematopus", exude a latex when the stem is broken, and many species have a chlorine-like odor.
Overview.
"Mycenas" are hard to identify to species and some are distinguishable only by microscopic features such as the shape of the cystidia. Some species are edible, while others contain toxins, but the edibility of most is not known, as they are too small to be useful in cooking. "Mycena pura" contains the mycotoxin muscarine.
Over 33 species are known to be bioluminescent, creating a glow known as foxfire. These species are divided among 16 lineages, leading to evolutionary uncertainty in whether the luminescence developed once and was lost among many species, or evolved in parallel by several species. One advantage of bioluminescence may lie in its potential to attract insects that can disperse the mushroom's spores.
Alexander Smith's 1947 "Mycena" monograph identified 232 species; the genus is now known to include about 500 species worldwide. Maas Geesteranus divided the genus into 38 sections in 1992, providing keys to each for all the species of the Northern Hemisphere. Many new species have been discovered since then, and four new sections have been proposed. Taxonomy is complex, as most sections are not truly homogeneous, and the keys fail for some species, especially those that satisfy some criteria for only part of their life cycle. Some sections contain only one species.
The name "Mycena" comes from the Ancient Greek μύκης ', meaning "fungus." Species in the genus "Mycena" (and in "Hemimycena") are commonly known as bonnets.