Summary:
The principal fieldmarks are 1) small size, 2) a hygrophanous, orange-yellow to dull butter yellow cap surface, 3) a scalloped cap margin, 4) adnate to decurrent gills, 5) a pubescent stem, and 6) fruiting in tundra and alpine habitats, in association with the gray-green foliose to squamulose lichen Coriscium viride. Coriscium viride is regarded as a synonym of Lichenomphalia hudsoniana. The gray green, foliose to squamulose structure is the vegetative stage, the mushroom is the reproductive stage, and the joint organism forms a basidio-lichen. Lichenomphalia hudsoniana is a common mushroom lichen according to Brodo(1).

Cap:
0.8-2.3cm across, convex at first but disc soon shallowly depressed, expanding to broadly convex, finally flat or rarely broadly funnel-shaped; hygrophanous, bright orange-yellow when moist, fading very slowly to whitish; surface bald "or with white pubescence about the disc, somewhat waxy-appearing at times, moist"; margin crenate [scalloped], "faintly pellucid-striate at times", (Bigelow), white, cream, to dull butter yellow, (Laursen)

Flesh:
thin, rather brittle; colored as cap surface and fading in a similar manner, (Bigelow)

Gills:
"adnate at first, soon becoming short decurrent, finally moderately decurrent, subdistant to distant", broad (0.3-0.4cm), separable from the cap flesh; near the color of the moist cap but not fading; waxy-appearing, edges even, (Bigelow)

Stem:
1.5-2cm x 0.15-0.3cm, fistulose [hollow], usually equal, often curved; white-pubescent, translucent white to pallid or pale orange-yellow, beneath the pubescence; "base with a small amount of white tomentum", (Bigelow), whitish, buff light tan to light olive, "always fruiting from a gray-green foliose to squamulose lichen thallus", (Laursen)

Odor:
not distinctive (Bigelow)

Taste:
not distinctive (Bigelow)

Microscopic spores:
spores 6-8(9) x 4-5(6) microns, usually elliptic, sometimes obovate or oblong, smooth, inamyloid; basidia usually 4-spored (at times 2-spored), 29-37(52) x 5.5-8 microns; cystidia usually not differentiated; clamp connections absent, (Bigelow), spores 8.5-10 x 4.5-5.2 (Laursen(1) who give 7-8 x 6-7 microns for Lichenomphalia umbellifera)

Spore deposit:
pale buff to pale orange-yellow (Bigelow)

Notes:
Lichenomphalia hudsoniana has been found in BC (collections at University of BC by I.M. Brodo and by Trevor Goward as Phytoconis viridis). It has been found in NF, NU, QC, AK, NH, NY, and VT, (Bigelow). It is a circumpolar species that dips down the western Rocky and Cascade Mountain ranges and eastern mountains, (Laursen).

EDIBILITY

Synonyms and Alternate Names:
Clitocybe hudsoniana (H.S. Jenn.) H.E. Bigelow
Gerronema hudsonianum (H.S. Jenn.) Singer
Hygrophorus hudsonianus H.S. Jenn.
Omphalia luteolilacina J. Favre
Omphalina hudsoniana (H.S. Jenn.) H.E. Bigelow
Omphalina luteolilacina (J. Favre) D.M. Hend.
Phytoconis hudsoniana (H.S. Jenn.) Redhead & Kuyper