E-Flora BC: Electronic Atlas of the Flora of British Columbia

Summary:
Adoni-minutive. Courtecuisse places in Section Aciculae, Smith in Subsection Aciculae of Deminutivae. However, there is some evidence it is not a Mycena and will need an new genus (D. Miller, pers. comm.). Mycena acicula is characterized by bright color that begins as coral red and fades to yellow, non-marginate gills (but may have white edges), slender stature, large subfusoid spores, and cystidia. Maas Geesteranus notes "It is precisely because of the pseudoparenchymatous structure of its hypoderm that I would not be surprised one day to see M. acicula segregated from Mycena and placed in a genus of its own" [Latin names in italics].

Smith studied collections from WA, OR, ON, AL, NC, MI, and France, and said that it "probably occurs" in BC (but doubts Davidson''s report). There is a Scott Redhead collection from BC at the University of British Columbia. Desjardin(6) lists it for CA. Maas Geesteranus mentions it for northern Africa.

Cap:
0.3-0.7(1)cm across, convex or bell-shaped, sometimes expanding when old; "coral-red when young, soon fading (often from margin inward) to bright orange-yellow or yellow"; not viscid, (Arora), 0.3-1cm across, obtuse or convex when young, becoming broadly convex or bell-shaped, sometimes with a small abrupt umbo, margin appressed against stem when young, often flaring or recurved [upcurved] as expansion takes place, a narrow sterile band that frequently becomes lobed or lacerated often forming the extreme edge; not hygrophanous, "coral red" [Ridgway(1) color] when young, soon yellowish toward margin, slowly fading to bright orange yellow; smooth, at first hoary-pruinose, soon bald, faintly translucent-striate when moist, (Smith), slightly viscid (with dirt sticking to surface), (Maas Geesteranus)

Flesh:
very thin; yellow, (Arora), thin, brittle; yellow, (Smith), thin, orange-red in cap, yellow in stem, (Maas Geesteranus)

Gills:
"attached (usually adnate)"; "pale orange to yellow or whitish", (Arora), adnate or slightly rounded next to stem, close to subdistant, 10-14 reaching stem, 2-3 tiers of subgills, gills moderately broad; pale orange to whitish, often yellowish at base and whitish along the edges, (Smith), ascending, 9-16 reaching stem, about 0.1cm broad, somewhat ventricose; deep orange yellow near base, paler toward edge, becoming pale, the edge whitish; not veined, (Maas Geesteranus)

Stem:
1-7cm long and less than 0.1cm wide, thread-like, equal, brittle; "orange-yellow to yellow"; "smooth except for hairy base", (Arora), 1-6cm long and up to 0.1cm wide, flexuous [wavy], brittle; densely white-pruinose at first but soon bald and orange-yellow or lemon yellow; base strigose with white hairs, (Smith), somewhat viscid, (Maas Geesteranus)

Odor:
mild (Arora), not distinctive (Smith)

Taste:
not distinctive (Smith)

Microscopic spores:
spores 9-11 x 3.5-4.5 microns, elongated-elliptic, smooth, inamyloid, (Arora), spores 9-11 x 3.5-4.5 microns, subfusoid [somewhat spindle-shaped], inamyloid; basidia 4-spored, 20-22 x 5-6 microns; pleurocystidia and cheilocystidia similar, (the latter inconspicuous and the former projecting only slightly), 25-32 x 6-9 microns, clavate to subfusoid or obovoid, tips often covered with a resinous secretion (when revived in KOH), (Smith), "hyphae of pileipellis 2.5-3.5 microns wide, clamped, overlying a pseudoparenchymatous hypoderm, covered with simple, cylindrical excrescences 2-9 x 1-3 microns (the gelatinous matter covering the excrescences no longer visible in microscopic slides)", (Maas Geesteranus)

Spore deposit:
white (Arora)