Summary:
Mycoacia nothofagi is distinguished particularly by soft, brittle teeth and abundant, thick-walled, encrusted cystidia (Nakasone(11) who says it is variable in form and color but shows little variation in microscopic characters). Other features include flat growth on hardwoods, a somewhat waxy surface with soft white membranous flesh, the surface color shades of brown, orange-brown, orange, gray-brown, or yellowish brown, often darker between and at base of teeth, the teeth 0.1-0.6cm long and glaucous to velvety, the margin of the fruitbody lighter in color. The description is derived from Nakasone(11).

Microscopic:
SPORES (4.5)5-5.5(6) x 2.2-2.5(2.9) microns, elliptic, "adaxial side straight or slightly concave", smooth, inamyloid, the walls colorless, thin, distinct; BASIDIA 4-spored, 20-32(36) x 4-6 microns, clavate, tapering to 2-2.5 microns wide at base, with basal clamp connection; CYSTIDIA of two types 1) tramal - fusiform, rarely cylindric, with a long stalk, up to 180 microns long, 3.5-8(14) microns wide including crystals, tapering to 3.5-4 microns wide at base, with basal clamp connection, "often with secondary septa, apex acute to rounded", walls colorless to yellowish brown, "thin throughout but sometimes slightly thickened at distal end, smooth or lightly to moderately encrusted at apex" with colorless, "loosely adherent, coarse, crystalline materials", "originating in subiculum or tooth trama, often curving into subhymenium and hymenium", becoming embedded or protruding up to 55 microns beyond the hymenium, "also extending into tooth apex, numerous in tooth trama", 2) hymenial - cystidia fusiform, 35-90 x 5-7 microns, tapering to 1.5-2.5 microns wide at base, with basal clamp connection, walls colorless, slightly thickened, up to 0.1cm thick, but often thinning at base, "basal part smooth, distal part lightly to moderately encrusted" with closely adherent, colorless crystalline materials, "embedded or protruding" up to 45 microns, "arising from subhymenium, numerous in subhymenium and hymenium"; HYMENIUM "a dense palisade of basidia and cystidia, not agglutinated but difficult to separate individual elements, occasionally interspersed with clumps of reddish brown, resinous materials"; SUBHYMENIUM thickening, 25-80 microns thick between teeth and near apices of teeth, up to 300 microns thick at base of teeth, "hyphae oriented perpendicular to substrate or to long axis of teeth, dense, compact, agglutinated, often indistinct and collapsed", hyphae 2-3.5 microns wide, nodose-septate, "frequently branched, conglutinate, short-celled", walls colorless, thin, smooth; TOOTH HYPHAE - teeth with "central core of vertically arranged, parallel, subicular hyphae that may be smooth or encrusted, and smooth or encrusted cystidia enclosed by subhymenium and hymenium", sometimes with elongate clusters of acerose or flattened, colorless crystals and resinous materials, "often with cystidia protruding at apex and through hymenium"; SUBICULUM of smooth areas between teeth up to 900 microns thick, "sometimes stratose, with a very thin, yellow-orange basal layer", up to 50 microns thick, "of agglutinated hyphae arranged parallel to substrate and a thicker layer of non-agglutinated hyphae, first arranged more or less parallel to substrate in a loose, open textura intricate that develops into a dense vertical palisade near subhymenial interface", hyphae 2.5-5.5 microns wide, rarely orange, nodose-septate, "sparingly to moderately branched, often branching from clamps and forming H-connections", walls colorless, "thin to slightly thickened, smooth"; HYPHAE monomitic

Notes:
Collections were examined from BC, WA, ID, CA, DC, FL, LA, MT, NC, NY, TN, WI, Azerbaijan, Macedonia, Czech Republic, France, Georgia, Germany, Russia, Slovak Republic, Spain, Switzerland, United Kingdom, Australia, and New Zealand, (Nakasone(11) who says also reported from Portugal, Romania, and Thailand).