Rickenella fibula
https://www.mushroomexpert.com/Rickenella_fibula.html
Ecology: Probably saprobic but apparently involved in some sort of mutualism with moss; growing alone, scattered, or gregariously in moss beds; spring through fall, or over winter in warm climates; widely distributed in North America. The illustrated and described collections are from Illinois.
Cap: 2-10 mm across; blocky or squarish at first, becoming convex, then broadly convex, with or without a shallow central depression; tacky when fresh but soon dry; bald or, with a hand lens, very finely hairy; the margin translucent-lined by maturity; orange with a whitish margin when fresh and young; soon fading to yellowish orange overall, with a darker orange center.
Gills: Running deeply down the stem; distant or nearly so; short-gills in several tiers; creamy or very pale orange.
Stem: 5-45 mm long; 0.5-1.5 mm thick; equal; dry; bald; colored like the cap; basal mycelium white.
Flesh: Insubstantial; pale.
Odor and Taste: Not distinctive
Chemical Reactions: KOH negative on cap surface.
Spore Print: White.
Microscopic Features: Spores 3-4 x 1.5-2.5 m; ellipsoid; smooth; hyaline and 1- to 3-guttulate in KOH; inamyloid. Cheilocystidia and pleurocystidia 25-40 x 5-7.5 m; fusiform with tapered or subcapitate apices; thin-walled; hyaline in KOH; smooth. Pileipellis a tightly packed cutis with numerous pileocystidia 50-100 x 7.5-12.5 m, fusiform with wide bases and tapered, subcapitate, or capitate apices, thin-walled, smooth, hyaline in KOH.
but its use with mushrooms is mine.
**Scientists identify most bitter substance ever known**
