Mycena Overholtsii
History and naming
The species was first described by mycologists Alexander H. Smith and Wilhelm Solheim in 1953, on the basis of specimens collected in the Medicine Bow Mountains of Albany County, Wyoming. The specific epithet honors the early 20th-century American mycologist Lee Oras Overholts. It is commonly known as the "snowbank fairy helmet", or "fuzzy foot", although it shares the latter name with Tapinella atrotomentosa and Xeromphalina campanella. M. overholtsii has been given the Japanese name yukitsutsumikunugitake.
Description
Mycena overholtsii produces some of the largest mushrooms of the genus Mycena. They have caps that are 1.5 to 5 cm (1⁄2 to 2 in) in diameter, and convex in shape, developing an umbo (a central protrusion resembling a nipple) in maturity. The cap surface is smooth, moist, and marked with radial striations. The caps are somewhat hygrophanous, and depending on age and state of hydration, range in color from brown or grayish-brown, to dark or bluish-gray. The mushroom flesh is thin and watery, with a light gray color.
The gills have an adnate, adnexed, or shallowly decurrent attachment to the stem, and are initially closely spaced before becoming well-spaced at maturity. They have a whitish to pale gray color, and will stain gray when they are bruised. There are three or four tiers of lamellulae (short gills that do not extend fully from the cap margin to the stem) interspersed between the gills. The stem is 4 to 15 cm (1+1⁄2 to 6 in) long by 0.3 to 1 cm (1⁄8 to 3⁄8 in) thick, and tapers upward so that the stem apex is slightly thinner than the base. It can be straight or curved, has cartilage-like flesh, and is hollow in maturity. When growing on soft, well-decayed wood, the stem often penetrates deeply into the substrate. The stem is pinkish-brown in color, and the lower half is tomentose – densely covered with white, woolly hairs. The mushroom has a yeast-like odor and a mild taste; its edibility is unknown, but it is not considered poisonous.
Microscopic characteristics
Viewed in deposit, as with a spore print, the spores appear white. Microscopically, the spores are roughly elliptical, sometimes appearing bean-shaped, with dimensions of 5.5–7 by 3–3.5 μm. They are thin-walled and smooth, and bear an indistinct hilar appendage. The spores are amyloid, meaning they will absorb iodine and turn black to blue-black when stained with Melzer's reagent. The basidia (spore-bearing cells) are four-spored. The cheilocystidia (cystidia on the gill edge), which are scattered and interspersed with basidia, are roughly cylindric to fusoid (spindle-shaped), smooth, hyaline (translucent), and measure 45–65 by 2–5.5 μm. Pleurocystidia (cystidia on the gill face) are uncommon, and similar in appearance to the cheilocystidia. The cap cuticle is an ixocutis (a fungal tissue type in which the hyphae are gelatinous and lie flat) with mostly smooth hyphae that are 1.5–3.5 μm in diameter. The cap flesh is dextrinoid, meaning it will turn reddish-brown in Melzer's reagent. Clamp connections are present in the hyphae of M. overholtsii.