Summary:
Section Deminutivae (Smith), Section Oregonenses (Maas Geesteranus). However, there is some evidence it is not a Mycena and will need an new genus (D. Miller, pers. comm.). Features include 1) small size, 2) a moist striate cap that is bright yellow at first on disc and deeper on the margin, 3) yellow or orange or whitish gills with darker yellow edges, 4) a dry, yellow stem covered with downy yellowish hairs, 5) growth on individual conifer needles, 6) a white spore deposit, and 7) elongate spores.

Cap:
0.2-1cm across, parabolic to convex; bright yellow, hardly fading with age, (in European specimens the color is more orange or even orange-red); moist, not lubricous, faintly translucent-striate, delicately pruinose, becoming bald, (Maas Geesteranus), 0.2-1cm across, tiny, obtusely conic to convex, often with a papilla, margin appressed against stem then flares and becomes wavy when old, frequently with broken edges; "capucine yellow" on disc, "deep chrome" toward margin; faintly hoary then polished, finely striate when moist, opaque after losing moisture, (Smith), 0.2-1cm across but usually less than 0.5cm, obtusely conic to bell-shaped with papilla, margin flaring and becoming wavy when old; bright orangy yellow to yellowish when older; moist, faintly hoary then polished, transparently grooved, (Phillips)

Flesh:
thin, brittle; yellowish, (Maas Geesteranus, Smith)

Gills:
broadly adnate, decurrent with a tooth, ascending, 9-16 reaching stem; pale greenish yellow or whitish, the edge bright yellow, (Maas Geesteranus), adnate developing decurrent tooth, distant to subdistant though sometimes appearing close depending on how subgills develop, 10-12 gills reaching stem, up to 3 rows of subgills, gills narrow, broadest at point of attachment; "massicot yellow" or appearing whitish, edge "deep chrome" or nearly white when old, (Smith), "orange with darker edges in young specimens", (Phillips)

Stem:
1-3cm x 0.05-0.07cm, hollow, fragile, straight to flexuous [wavy], round in cross-section; colored as cap or paler yellow; not glutinous when wet, covered all over with yellowish pruinose-pubescence, becoming bald except at top, the base covered with coarse yellow fibrils, (Maas Geesteranus), 1-3cm x 0.05-0.07cm, equal, not fragile, base inserted on needles; colored as cap or paler, "evenly colored with a faint yellowish pubescence or pruinosity", base with scattered yellow hairs, (Smith)

Odor:
not distinctive (Maas Geesteranus, Smith)

Taste:
not distinctive (Maas Geesteranus, Smith)

Microscopic spores:
spores 7-10 x 2.5-4 microns, in the 2-spored variety this is 8-10 x 3.5-4 and in the 4-spored 7-8 x 2.5-3 microns [but Maas Geesteranus remeasured the width in holotype as 3.6-4.4 microns], subcylindric [nearly cylindric], tapered to a point at one end, often slightly curved, inamyloid; basidia either 2-spored or 4-spored (predominantly 2-spored in Europe according to Maas Geesteranus, and hyphae and cystidia in Europe said to be without clamp connections); cheilocystidia abundant, 30-45 x 9-12 microns, subcylindric to fusoid-ventricose, smooth or rarely forked at top, outlines often wavy, filled with bright yellow substance, pleurocystidia similar, scattered to rare, often very difficult to locate on sections of revived material, (Smith)

Spore deposit:
white (Phillips)

Notes:
Mycena oregonensis is found at least in WA, OR, CA, (Smith), and Europe (Maas Geesteranus). There are collections from BC at the Pacific Forestry Centre and the University of British Columbia.

EDIBILITY

unknown (Phillips)