Summary:
Features include 1) irregular hemispheric to cushion-shaped fruitbodies that are very common on recently dead alder, 2) color that is purplish to brown vinaceous, blood color, chestnut, or fuscous, with regularly set, darker perithecial ostioles, the surface even with perithecial elevations not prominent, 3) spores that are elliptic-inequilateral, and brown, with the germ slit the length of the spore, borne in 8-spored asci. "This fungus is on almost every limb of Alnus that has recently died anywhere in the North Temperate Zone. The hemispherical shape of the stroma is due to being usually on small limbs with bark" (Miller, J.H., the word Alnus italicized).

Microscopic:
SPORES 8-20 x 4-8 microns, elliptic-inequilateral, with narrowly rounded ends, unicellular, brown to dark brown, with slightly sigmoid germ slit spore-length, "perispore dehiscent in 10% KOH, smooth or with inconspicuous coil-like ornamentation", epispore smooth; ASCUS 85-202 x 6-9(12) microns, the spore-bearing part 60-115 microns long, stem 20-100 microns long, with apical ring blueing to lightly blueing in Melzer''s reagent, discoid, 0.5-2 microns high and 1.2-3.5 microns broad; PERITHECIUM 100-300(400) microns across and 200-500 microns high, spherical to obovoid, ostioles lower than stromatal surface, (Ju), SPORES 12-15 x 5-8 microns, inequilaterally elliptic, nearly opaque, uniseriate or obliquely uniseriate; ASCUS 70-96 x 8-9.6 microns in spore-bearing part, cylindric, with stem 60-70 microns long; PARAPHYSES copious; PERITHECIUM 150-300 microns in diameter, small, spherical to angular from compression, "with umbilicate, impressed ostiola"; CONIDIA 4-5 x 3 microns, elliptic, colorless, (Miller, J.H.), SPORES 12-13 x 5-6 microns, irregularly elliptic, somewhat flattened on one side, "smooth, dark brown, with a germination cleft", uniseriate; ASCUS 8-spored, 130-140 x 8 microns, amyloid; no PARAPHYSES observed; PERITHECIUM 300-400 microns, "black, evenly embedded in one layer in a superficially red-brown stroma", (Breitenbach)

Notes:
Hypoxylon fuscum has been found in WA, OR, ID, AK, AL, CA, CO, CT, DC, DE, FL, GA, IA, IN, KY, LA, MA, MD, ME, MI, MO, MT, NC, ND, NE, NJ, NY, OH, PA, SC, TN, TX, VA, VT, WI, WV, Canada (including NF), Austria, Belgium, Finland, France, Germany, Hungary, Italy, Latvia, Poland, Sweden, Switzerland, United Kingdom, China, and Japan, (Miller, J.H.). It has also been found in BC, ON, Guyana, Philippines, and Taiwan, (Ju).

Synonyms and Alternate Names:
Odontia nothofagi G. Cunn.
Phlebia nothofagi (G. Cunn.) Nakasone