Bulbous bonnet

Appearance

The cap of ''M. stylobates'' is 3–15 mm in diameter, and depending on its age may range in shape from obtusely conic to convex to bell-shaped to flattened. The structure of the cap margin also depends on the age of the mushroom, progressing from straight or curved inward slightly, to margin flaring or curved backward. The cap surface is smooth, although if viewed with a magnifying glass, minute spines can be seen. As it ages, the surface becomes smooth, moist and somewhat glistening, and it shows grooves corresponding to the position of the gills underneath the cap. The cap color is evenly pale watery gray. The flesh is thin, pallid, and has no distinguishable odor or taste.

The gills appear closely spaced in unexpanded caps, but usually more distant in old individuals. Between 8 and 16 gills extend from the margin to the stipe; there are additionally one or two tiers of small gills that do not reach fully from the margin to the stipe. The gills are narrow but become ventricose and sometimes very broad in age, and are attached by a line or are very narrowly adnate. Sometimes the gills split away from the stipe while remaining attached to each other; in this way they form a collar around the stipe. Gills are pale gray but soon become whitish, with even edges. The stipe is 10–60 mm long, 0.5–1 mm thick, and, above the level of the flat circular disc at the base, is equal in width throughout. The stipe is covered with fine white scattered fibrils, or is delicately pruinose , but it later becomes smooth. Its color is bluish-gray when fresh but soon it fades to gray. The basal disc is grooved and pruinose or covered with fine minute hairs, but soon becomes smooth. The insubstantial fruit bodies are considered inedible.The spores are 6–10 by 3.5–4.5 μm, narrowly ellipsoid, and faintly amyloid. The basidia are four-spored, rarely two-spored. The pleurocystidia are not differentiated. The cheilocystidium are abundant and variable in structure, usually club-shaped with between two to five thick obtuse projections that arise from near the apex, sometimes more or less covered with numerous protuberances over the enlarged portion and the neck more or less contorted. They measure 26–38 by 8–13 μm, and are hyaline. The gill flesh is made of greatly enlarged cells, and stains pale vinaceous in iodine. The flesh of the cap has a pellicle which usually gelatinizes in potassium hydroxide or water mounts prepared for microscopy. The surface hyphae are covered with short rodlike projections. Sometimes some of the hyphae become aggregated into peglike structures that project from the surface, and cause the appearance of scattered coarse spines on the cap when viewed under a 10X magnifying lens. The tissue beneath the pellicle is made entirely of greatly enlarged cells, which appear pale vinaceous in iodine stain.

The mycelia of ''M. stylobates'', when grown in pure culture, is bioluminescent, a phenomenon first reported in 1931. The fruit bodies are not known to be bioluminescent.

Naming

There are several species of ''Mycena'' that have a basal disc similar to ''M. stylobates''. ''Mycena mucor'' is usually smaller than ''M. stylobates'', and grows on fallen, decaying leaves of oak. It has different cheilocystidia, with very slender excrescences. Also, the margin of the basal disc is not ciliate like ''M. stylobates''. ''M. bulbosa'', a species that grows on woody stalks in wet habitats, has nonamyloid spores, and gill edges that contain a tough-elastic, gelatinous thread. ''M. pseudoseta'', described as a new species from Thailand in 2003 forms smaller fruit bodies with differently shaped cheilocystidia and cap hyphae.

Distribution

The fruit bodies of ''Mycena stylobates'' grow scattered or in groups on oak leaves or coniferous needles, in the spring and summer or early autumn. It is common during warm, wet seasons. ''Mycena'' specialist Alexander H. Smith has collected it in Tennessee, Michigan, Idaho, and Washington in the United States, and in Nova Scotia and Ontario in Canada. It is also found in Europe, including Britain, Denmark, Germany, Norway, Poland, Romania, Scotland, Serbia, Sweden, and Turkey. Although it has been reported several times from Australia, mycologist Cheryl Grgurinovic concluded in a 2003 publication that the records "are best regarded as erroneous".

Habitat

The fruit bodies of ''Mycena stylobates'' grow scattered or in groups on oak leaves or coniferous needles, in the spring and summer or early autumn. It is common during warm, wet seasons. ''Mycena'' specialist Alexander H. Smith has collected it in Tennessee, Michigan, Idaho, and Washington in the United States, and in Nova Scotia and Ontario in Canada. It is also found in Europe, including Britain, Denmark, Germany, Norway, Poland, Romania, Scotland, Serbia, Sweden, and Turkey. Although it has been reported several times from Australia, mycologist Cheryl Grgurinovic concluded in a 2003 publication that the records "are best regarded as erroneous".