E-Flora BC: Electronic Atlas of the Flora of British Columbia

Summary:
Features include 1) spherical to hemispheric fruitbodies that may coalesce, growing on hardwood, 2) color that is brick red or fulvous darkening to almost black, the surface having inconspicuous perithecial mounds near the periphery with umbilicate openings, the texture fleshy-leathery to woody, and the interior satiny black, 3) orange red granules immediately below surface, and white granules between perithecia, 4) KOH extractable pigments that are orange or rust, and 5) spores that elliptic-inequilateral and brown, with a slight germ slit spore-length on the convex side.

Hypoxylon howeanum has been found in WA, OR, AL, CT, DE. DC, FL, GA, IA, IN, KY, LA, MA, MD, ME, MI, MN, MS, NC, NE, NH, NJ, NY, OH, PA, SC, TN, VA, WI, WV, Canada, Cuba, Jamaica, Brazil, Chile, France, Germany, Sweden, United Kingdom, Africa, China, Japan, Sri Lanka, and Australia, (Miller, J.H.(1)). It is found in MA, NY, VT, Mexico, France, Germany, Italy, India, Japan, South Africa, Australia, and New Zealand, (Ju). It has been reported from BC (Redhead).

Fruiting body:
stromata [fruitbodies] 0.2-1.1(2.0)cm across and (0.06)0.15-0.8cm thick, hemispheric to spherical, "sessile or nearly so, with inconspicuous to conspicuous perithecial mounds"; surface fulvous, rust, or dark brick; orange red granules immediately beneath surface, with KOH-extractable pigments orange or rust; white granules between perithecia; the tissue below the perithecial layer black, up to 0.75cm thick, (Ju), stromata (fruitbodies) 0.3-1.2cm across, 0.3-0.8cm thick, spherical to hemispheric and symmetric except when crowded, "then tending to coalesce, but never widely effused", texture fleshy-leathery to woody, never carbonous; bright brick-red, varying to reddish purple or brown and when old darkening to almost black, perithecia small, in periphery of stroma, opening by umbilicate ostiola that do not protrude beyond the surface; interior "satiny black with one or more faint concentric zones", (Miller, J.H.)

Microscopic:
SPORES 7-9.5 (10) x 3-4.5 microns, elliptic-inequilateral, with narrowly rounded ends, brown to dark brown, unicellular, "with slight sigmoid germ slit spore-length", perispore dehiscent in 10% KOH, smooth, epispore smooth; ASCUS 80-130 x 4.5-6.3 microns, the spore-bearing part 50-70 microns long, the stem 30-77 microns long, with apical ring turning blue in Melzer''s reagent, discoid, 0.4-0.8 microns high and 1.2-2 microns broad; PERITHECIUM 100-300 microns in diameter and 200-400 microns high, spherical to obovoid, ostiole "lower than or at the same level as the stromatal surface", (Ju), SPORES 6-9 x 3-3.5 microns, inequilaterally elliptic, almost opaque, "obliquely monostichous" [in one line or series]; ASCUS 50-60 microns x 5-6 microns in spore-bearing part, elongate, cylindric, with stem 40-50 microns long; PERITHECIUM 200-300 microns in diameter; CONIDIA on surface of stroma 4-6 microns in diameter, round to oblong, colorless, (Miller, J.H.)