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Species Information
Summary: Features include 1) resupinate growth on the underside of dead branches and trunks of hardwoods, 2) dense spines that are waxy, yellow to ochraceous, the tip usually smooth, the margin of the fruitbody with smaller spines and ending smoothly, sometimes pruinose or rather fringed, 3) the young yellow parts of the fruitbody turning deep red with drops of KOH, 4) narrowly elliptic spores that are smooth and inamyloid, 5) cystidia present as small subfusiform cystidioles somewhat projecting beyond the hymenium, and 6) a monomitic hyphal system, the hyphae with clamp connections.
Mycoacia uda has been found in BC, WA, OR, MB, ON, IA, IN, LA, MI, MT, NY, TN, and WI, (Ginns(5)). Distribution includes BC, WA, OR, ID, MB, ON, QC, IA, IL, MT, NY, SD, TN, VA, WI, Armenia, Austria, Azerbaijan, Czech Republic, Denmark, Estonia, France, Georgia, Germany, Italy, Netherlands, Russia, Spain, Sweden, and Turkmenistan, (Nakasone(11) who says also reported from Portugal, Turkey, Iran, Ethiopia, and Morocco). Distribution includes Switzerland (Breitenbach), and Denmark, Finland, Norway, and Sweden, (Eriksson).
Fruiting body: resupinate, adnate [firmly attached], effused [spread out], "mostly of small to moderate size", citrine to sordid yellow, when old ochraceous; aculei [spines] conic to subcylindric, ceraceous [waxy], mostly 0.1-0.2cm long, seldom more, "as a rule simple, but sometimes apically divided or basally joined"; margin thinning out, pruinose or finely fimbriate [fringed] under lens; "subiculum thin, fertile only in the marginal part"; "young yellow parts of the fruitbody turn deep red in a drop of KOH", (Eriksson), resupinate, tightly attached, forming expanses several centimeters across, more rarely several decimeters; thin, wax-like subiculum from which arise densely crowded, slender, pointed spines that are 0.1-0.2cm long, usually single but here and there fused at the base, sulfur-yellow, wax-yellow, or ocher-yellow, tips smooth or more rarely somewhat fringed; margin "with shorter spines and ending smoothly, sometimes rather fringed or farinose"; KOH colors the fruitbody purple-red, (Breitenbach), spore deposit white (Buczacki)
Microscopic: SPORES 5-6 x 2-2.5 microns, narrowly elliptic, smooth, inamyloid, acyanophilic, thin-walled, often with 1-2 small oil droplets; CYSTIDIA present as small cystidioles, about 25 microns long, subfusiform, "somewhat projecting and apically provided with a cap of non-crystalline matter, easily dissolved in mounting media"; HYPHAE monomitic, hyphae 2-3 microns wide, with clamp connections, "with thin or slightly thickened walls", packed in parallel fashion in the aculeal trama, "subhymenial hyphae densely intertwined"; "in mature specimens aculeal trama filled with rod-like crystals, in old specimens often united to larger lumps", "in such specimens apical hyphae end more or less encrusted", (Eriksson), SPORES 5-6 x 2-3 microns, oval, smooth, inamyloid, colorless, with 1-2 droplets; BASIDIA 4-spored, 15-20 x 4-5 microns, narrowly clavate; CYSTIDIA inconspicuous, 20-25 x 4 microns, fusiform; HYPHAE monomitic, 2-3 microns wide, some with clamp connections; CRYSTALS in the trama of the aculei, (Breitenbach)
Habitat / Range
on "underside of dead branches and trunks of hardwoods, with and without bark", throughout the year but matures only in the summer half, (Breitenbach), on much decayed hardwood, (Eriksson), Acer (maple), Alnus (alder), Arbutus (madrone), Cytisus scoparius (broom), Fagus (beech), Fraxinus (ash), Populus, Pseudotsuga (Douglas-fir), Quercus (oak), Salix (willow); associated with a white rot, (Ginns)
Similar Species
Mycoacia fuscoatra has a pale yellow to ochraceous spore-bearing surface that stains red to purple in KOH on the yellow parts, and its spores are subcylindric and only 1.7-2.5 microns wide, whereas M. uda has a distinctly yellow spore-bearing surface, the yellow parts staining red in KOH, and spores are narrowly elliptic and 2-3(3.2) microns wide, (Ginns(23)). In M. fuscoatra 1) mature fruitbodies are dark brown to almost black rather than ochraceous as in M. uda, 2) apical hyphae are strongly encrusted, conspicuous, and cystidia-like in mature specimens (in M. uda encrusted hyphae if present are few and inconspicuous), 3) cystidioles are acicular, whereas those of M. uda are short, and not acicular, and 4) yellow, oily bodies are present in cotton-blue, (Eriksson). Mycoacia aurea does not stain in KOH, (Ginns(23)). M. aurea 1) does not stain red in KOH when young like M. uda, 2) has spores that are shorter and suballantoid, and 3) normally lacks cystidioles, (Eriksson). Mycoacia austro-occidentale Canf., found in Arizona, is pale buff to cream, with spores measuring 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).
