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Species Information
Summary: Features include 1) resupinate growth on hardwood, 2) dense spines that are waxy, cream to yellow-ochraceous, often with branched tips, and as a rule serrate with lateral projections, 3) a fruitbody margin that is light colored with shorter spines and ending smoothly, 4) short allantoid spores that are smooth and inamyloid, 5) a monomitic hyphal system, the hyphae with clamp connections, and 6) absent cystidia and a negative KOH reaction.
Mycoacia aurea has been found in BC, ON, IA, MI, MN, NY, and SC, (Ginns(5)). Distribution includes OR, ON, MT, NC, WI, Costa Rica, Armenia, Austria, Czech Republic, Denmark, Estonia, Finland, France, Germany, Georgia, Lithuania, Norway, Russia, Slovak Republic, Spain, Sweden, Turkey, Ukraine, Iran, India, Japan, Uzbekistan, (Nakasone(11) who says also reported from Portugal and Korea). It occurs in Denmark, Finland, Norway, and Sweden, (Eriksson), and Europe (including Switzerland) and Asia, (Breitenbach).
Fruiting body: resupinate, effused [spread out], adnate [firmly attached], often rather large; aculei dense, 0.2-0.3cm long, subcylindric, often branched in 2 or 3 tips, as "a rule also serrate with small lateral projections", ceraceous [waxy], "creamish when young, yellow-ochraceous when mature"; margin light colored, "under the lens finely fibrillose or indeterminately thinning out", (Eriksson), resupinate, tightly attached, forming patches several centimeters across, surface consisting of thin wax-like subiculum, from which arise "crowded, slender, pointed spines", 0.1-0.2cm long, cream to pale yellow, ocher when old, "smooth or sometimes with small lateral outgrowths, ends usually with 2-3 small points", usually single but fused here and there at base; "marginal zone with shorter spines and ending smoothly"; KOH does not change the color of the fruitbody, (Breitenbach), spore deposit white (Buczacki)
Microscopic: SPORES 3.5-4.5(5.5) x 1.5-2 microns, suballantoid, adaxially concave, smooth, inamyloid, acyanophilic, thin-walled; BASIDIA 4-spored, 12-15(20) x 4-5 microns, in a dense palisade, narrowly clavate, with basal clamp connection; CYSTIDIA and cystidioles usually none but in one specimen near the tips of the aculei projecting hyphal end that could be designated as cystidioles; HYPHAE monomitic, the hyphae 2-3 microns wide, thin-walled, with clamp connections, "in the aculeal trama densely parallel, in the thickening subhymenium intertwined into a pseudoparenchymatic context, in the aculeal apices glued together to projecting bundles", when young the hyphal texture clean, but when old more or less loaded with crystals, (Eriksson), SPORES 4-5.5(6) x 1.5-2 microns, cylindric-elliptic [but some illustrated as curved], smooth, inamyloid, colorless; BASIDIA 4-spored, 13-15 x 3.5-4.5 microns, clavate, with basal clamp connection; CYSTIDIA not seen; HYPHAE monomitic, 2.5-4 microns wide, thin-walled to thick-walled, with clamp connections, sometimes "crystals are stored in old fruiting bodies", (Breitenbach)
Habitat / Range
on the underside of dead branches and trunks of hardwoods, summer to fall, (Breitenbach), on decayed hardwood (Eriksson), Alnus rubra (Red Alder), Populus sp., P. tremuloides (Quaking Aspen), Ulmus sp., (Ginns(5))
Similar Species
Mycoacia fuscoatra has a pale yellow to ochraceous spore-bearing surface that stains red to purple in KOH on the yellow parts, whereas M. aurea does not stain in KOH, (Ginns(23)). Mycoacia uda has a yellow spore-bearing surface, the yellow parts staining red in KOH, and narrowly elliptic spores 2.0-3.0(3.2) microns wide, (Ginns(23)). M. fuscoatra and M. uda have 1) longer spores that are straight, narrowly elliptic, or subcylindric, 2) cystidioles, and 3) spore-bearing surface red in KOH at least when young, (Eriksson). M. uda is hardly distinguishable by appearance but differs in KOH reactions and microscopic characters, (Breitenbach). Mycoacia austro-occidentale Canf., found in Arizona, is pale buff to cream, with spores that measure 4.0-4.5 x 2.0-2.5 microns, (Ginns(23)). Mycoacia is separated from other resupinate, odontioid fungi by its wax-like consistency, (Breitenbach).
