Summary:
Section Calodontes (Smith), Section Fragilipedes (Maas Geesteranus). Mycena citrinomarginata is very variable in all its distinguishing features: color of cap, color of gill edge, spore size and type of cheilocystidia, but nevertheless one of the easiest Mycenae to recognize, (Smith). Features include 1) a hygrophanous, striate cap that is grayish yellow to brownish yellow or bright yellow or even white, 2) gills that are whitish or ash-gray, with edges that are yellow when cap is yellow, and sordid brown when cap is brown, 3) a stem that is olivaceous gray or yellowish, 4) elongate spores, and 5) variable cheilocystidia. Smith recognized another species Mycena olivaceobrunnea, distinguished by its consistently smaller size and smaller spores 6.5-8 x 4-4.5 microns (8-10 x 4-5 microns in 2-spored variant). Maas Geesteranus remeasured spores to be 7.6-9.8 x 4.5-5.4 microns and does not recognize M. olivaceobrunnea, but Michael Beug (pers. comm.) reports M. olivaceobrunnea from the Pacific Northwest with spore size and color matching Smith''s description. (The cap color of M. olivaceobrunnea is given by Smith as "buffy brown" to "dark olive buff" [Ridgway(1) colors] with a pallid margin, fading to sordid yellowish gray.) The description here derived from Smith(1) for M. citrinomarginata except where noted.

Cap:
(0.5)1-3.5(4)cm across, conic, broadly convex, or conic - bell-shaped, with margin close to the stem and incurved when young, often flaring in maturity; hygrophanous, grayish yellow to brownish yellow or bright yellow or even white, fading to yellowish or olive gray (color may be lighter in shady areas and darker in exposed areas); surface pruinose becoming bald and polished, moist, translucent-striate, when old sulcate [grooved], (Smith), "pale yellowish, greyish yellow, pure yellow, sulphureous, greenish yellow, olivaceous yellow, yellowish with a brownish grey shade, greyish green, darker at the centre (ochraceous, orange-yellow, brownish yellow, grey-brown, pale date brown), paler toward margin, more rarely entirely white", (Maas Geesteranus), pale yellowish to olivaceous to date brown (Trudell)

Flesh:
thick on cap center of large caps but otherwise thin, fragile; grayish yellow to whitish

Gills:
ascending adnate, distant to subdistant, (14-20 reaching stem), 2-3 tiers of subgills, gills narrow, +/- 0.2-0.3cm, interveined; marginate: whitish or ash-gray with edges yellow (when cap yellow) to sordid brown (when cap brown), (Smith), whitish to yellow-gray usually with a lemon yellow edge, (Trudell)

Stem:
3-8cm x (0.05)0.1-0.25cm, equal, fragile, round in cross-section or compressed, hollow; olivaceous gray or yellowish, usually paler and brighter in upper part; "the apex pruinose at first, either smooth or somewhat striate", base somewhat mycelioid

Odor:
not distinctive

Taste:
not distinctive

Microscopic spores:
spores 8-14 x 4-6 microns: in 4-spored variety 8-11 x 4-5.5(6) microns, in 2-spored variant 12-14 x 5-6 microns, elliptic to subcylindric [nearly cylindric], amyloid, [presumably smooth]; basidia 2-spored, 3-spored, or 4-spored; pleurocystidia "absent or very rare to occasional", cheilocystidia abundant and variable, awl-shaped, fusoid-ventricose, or clavate, all of these types either smooth, variously branched, or with finger-like prolongations over the upper part, (Smith)

Spore deposit:
white (Phillips)

Notes:
Mycena citrinomarginata has been found at least in BC, WA, OR, ON, MB, CA, MI, and NY.

EDIBILITY

unknown (Phillips)

Synonyms and Alternate Names:
Mycena olivaceobrunnea A.H. Sm.