Goldenedge Bonnet

Appearance

The cap of "M. aurantiomarginata" ranges in shape from obtusely conic to bell-shaped, and becomes flat in maturity, reaching diameters of 0.8–2.0 cm. The cap color is variable, ranging from dark olive fuscous to yellowish-olive in the center, while the margin is orangish. Alexander H. Smith, in his 1947 monograph of North American "Mycena" species, stated that the caps are not hygrophanous, while "Mycena" specialist Arne Aronsen says they are. The overall color fades as the mushroom ages. The surface is moist, and young individuals are covered with fine whitish powder, but this soon sloughs off to leave a polished surface that develops radial grooves in maturity. The flesh is thin and flexible.

Gills are adnate with a decurrent tooth, and initially narrow but broaden when old. They are pallid to grayish-olive with bright orange edges. Smith noted that the edge color may spread to the gill faces in some specimens, because the pigment, rather than being encrusted on the walls of the cystidia, is found in the cytosol and therefore more readily diffusible. The gills are spaced close together, with between 16 and 26 gills reaching the stipe, and there are up to three tiers of interspersed lamellulae.

The cylindrical stipe is 3–6 cm long by 0.1–0.2 cm thick, hollow, and stiff but flexible; it is somewhat thicker at the base. It has a brownish to grayish-olive color that is sometimes tinged with shades of orange. The surface is smooth except for orange powder near the top, while the base is covered with stiff orange hairs. Smith reports the mushroom tissue to have no distinctive taste or odor, while Aronsen says the odor is "very conspicuous; sweet, fruity, often experienced as farinaceous or faintly of anise". Like many small "Mycena" species, the edibility of the mushroom is unknown, as it is too insubstantial to consider collecting for the table.

The spores are elliptic, smooth, and amyloid, with dimensions of 7–9 by 4–5 μm. The basidia are club-shaped, four-spored, and measure 25–32 by 5.5–7 μm. Pleurocystidia and cheilocystidia are abundant and similar in morphology: club-shaped to somewhat capitate, the tops sparsely to densely covered with small spines, filled with a bright orange pigment, and measuring 28–36 by 7–12 μm. The flesh of the cap is covered with a cuticle, on the surface of which are found scattered cystidia similar to those on the gills. Directly beneath the cuticle is a layer of enlarged cells, and beneath this are filamentous hyphae. Clamp connections are present in the hyphae.

"Mycena aurantiomarginata" uses a tetrapolar mating system, whereby genes at two different locations on the chromosomes regulate sexual compatibility, or mating type. This system prevents self-fertilization and ensures a high degree of genotypic diversity. When the fungal mycelia is grown in culture on a petri dish, the colonies are white, odorless, and typically have a central patch of congested aerial hyphae that grow upward from the colony surface, which abruptly become flattened to submerged, and occasionally form faint zone lines. The hyphae commonly form deposits of tiny amorphous crystals where they contact other mycelial fronts, especially where the hyphae are vegetatively incompatible and destroy each other by lysis.

Naming

"Mycena aurantiomarginata" is generally recognizable in the field by its olive-brown to orangish cap, bright orange gill edges, and yellowish hairs at the base of the stipe. "M. elegans" is similar in appearance to "M. aurantiomarginata", and some have considered them synonymous. "M. elegans" is larger, with a cap diameter up to 3.5 cm and stipe length up to 12 cm, darker, and has pale greenish-yellow colors on the gill edges and stipes that stain dull reddish-brown in age. "M. leaiana" is readily distinguished from "M. aurantiomarginata" by the bright orange color of its fruit bodies, its clustered growth on rotting wood, and the presence of a gelatinous layer on its stipe. "M. strobilinoides" closely resembles "M. aurantiomarginata" in shape, size, spore morphology, and the presence of hairs at the stipe base. It has a cap color that ranges from scarlet to yellow, and features scarlet edges on widely spaced, pale pinkish-orange to yellow gills.

Distribution

"Mycena aurantiomarginata" is a saprobic fungus, deriving nutrients from decomposing organic matter found on the forest floor, such as needle carpets. Fruit bodies of the fungus grow scattered, in groups, or in tufts under conifers, and are often found on moss. In North America, it is found in California, Washington, Oregon, and British Columbia, and the species is widely distributed in western and northern Europe. In Central America, the mushroom has been collected on the summit of Cerro de la Muerte in the Cordillera de Talamanca, Costa Rica, on leaf litter of "Comarostaphylis arbutoides". In 2010, it was reported from Hokkaido in northern Japan, where it was found growing on "Picea glehnii" forest litter in early winter. It has also been recorded from North Africa.

Habitat

"Mycena aurantiomarginata" is a saprobic fungus, deriving nutrients from decomposing organic matter found on the forest floor, such as needle carpets. Fruit bodies of the fungus grow scattered, in groups, or in tufts under conifers, and are often found on moss. In North America, it is found in California, Washington, Oregon, and British Columbia, and the species is widely distributed in western and northern Europe. In Central America, the mushroom has been collected on the summit of Cerro de la Muerte in the Cordillera de Talamanca, Costa Rica, on leaf litter of "Comarostaphylis arbutoides". In 2010, it was reported from Hokkaido in northern Japan, where it was found growing on "Picea glehnii" forest litter in early winter. It has also been recorded from North Africa.