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

Summary:
Hygrocybe acutoconica is distinguished by a bright yellow to orange, viscid cap with a persistently pointed umbo, adnexed to free yellow gills, a lubricous stem that is yellow to orange and may blacken at the base, and the absence of an overall blackening reaction. Breitenbach(3) gave this taxon as well as Hygrocybe constans Lange, Hygrocybe crocea Bres. and Hygrocybe langei Kuehner as synonyms of Hygrocybe persistens (Britzelm.) Britzelm. On the other hand, the online Species Fungorum, accessed January 17, 2016, gave Hygrocybe persistens (Britzelm.) Singer, Hygrocybe constans Lange, and Hygrocybe langei Kuehner as synonyms of Hygrocybe acutoconica (Clem.) Singer. Var. microsporus of Hygrophorus acutoconicus, described by Hesler(1) from TN, has smaller spores.

The type variety of Hygrocybe acutoconica was found in ID. BC collections are deposited at University of British Columbia. Oregon State university has collections from OR and ID. The University of Washington has a collection from MT. Material was also studied from FL, MI, MT, NC, NE, TE, TN, WY, and the Isle of Rhum, (Hesler(1)).

Cap:
2-7(10)cm across, bluntly or sharply conical when young, sometimes expanding when old but usually retaining pointed umbo; "bright yellow to yellow-orange or orange (the orange usually toward center)"; "smooth, viscid or slimy when moist", (Arora), 2-10cm across, obtusely to sharply conic when young, soon bell-shaped or the margin spreading or upturned; "waxy yellow", "cadmium yellow", "ochraceous buff", "ochraceous orange" to "rufous", scarcely fading; viscid or glutinous, bald, splitting radially, margin striatulate [finely striate] when wet, even when dry, (Hesler), if a touch of red occurs it is on tip or margin of cap, (Schalkwijk-Barendsen)

Flesh:
thin, soft, waxy; yellow, (Arora), thin on margin, thickish at center, soft; yellow in cap, (Hesler)

Gills:
adnexed to free, broad, thick, soft, waxy; yellow, never blackening, (Arora), free or narrowly adnexed, ascending, close becoming subdistant, moderately broad and ventricose [broader in middle]; yellow; edges sometimes eroded, faces wrinkled, (Hesler)

Stem:
5-8(12)cm x 0.3-0.6(1)cm, equal or wider in lower part, easily splitting; "yellow to yellow-orange, but usually white at base, not blackening when handled, but base may bruise or age grayish to nearly black"; "smooth, moist or slightly viscid", "usually longitudinally striate and/or twisted", (Arora), 6-8(12)cm x 0.3-0.6(1.2)cm, equal or nearly equal, round in cross-section or flattened, easily splitting; colored as cap, paler or white at base, not blackening when wounded but the base usually blackening when old; lubricous at times but not truly viscid (lacking gelatinous hyphae), fibrillose to bald, "striate, sometimes twisted-striate", (Hesler)

Veil:
absent (Arora)

Odor:
mild (Hesler)

Taste:
mild (Hesler)

Microscopic spores:
spores 9-15 x 5-9 microns, elliptic, smooth; gill tissue parallel, (Arora), spores 9-15 x 5-9 microns, 7-9(10) x 5-6 microns for variety microspora, elliptic, some irregular or constricted, smooth, inamyloid; basidia 1-, 2-, 3-, and 4-spored, 38-60 x 7-12 microns; pleurocystidia and cheilocystidia none; gill tissue parallel, hyphae 5-20 microns broad; clamp connections present, (Hesler)

Spore deposit:
white (Arora, Hesler)