Hypoxylon howeanum  

Anamorph: Nodulisporium-like, synnematous, buff to yellow-brown, with conspicuous mycelial columns 2-3 mm in length and 150-200 µm diam., composed of intertwined thick-walled yellow- to mid brown hyphae 2-4 µm diam., radiating from the base of young stromata. Conidiophores developing from the columnar tissue, frequently branched. Conidiogenous cells in small terminal clusters, 11-18 x 2-3 µm, ± cylindrical and tapered slightly towards the acute apex, rather irregular in outline, pale yellow, proliferating sympodially with minutely denticulate conidiogenous loci. Conidia 4-4.5(-6) x 2.5-3.5 µm, ellipsoidal to ovoid, hyaline, thin-walled, aseptate, smooth, without a gelatinous sheath or appendages.
Teleomorph: stromata 3-8 (-10) mm diam. x 2-6 mm tall, hemispherical to almost globose, usually  constricted at the base, aggregated in clusters and occasionally coalescent, the ascomata usually conspicuously domed with ± black ostioles that are either plane or slightly sunken, initially rust red and becoming dark grey-brown when old, with orange granules beneath the surface layer, KOH-extractable pigments orange to rust, initially with white granules between the ascomata, the tissue below the fertile layer black, extending upwards between the ascomata. Ascomata subglobose to pyriform, 200-400 µm diam x 300-500 µm tall. Interascal tissue composed of copious unbranched thin-walled paraphyses ca 2 µm diam, somewhat broader at the base, frequently breaking down at maturity of the asci. Asci 82-110 x 4-5.5 µm, cylindrical, very long-stalked (to ca 60 µm) fairly thin-walled, not fissitunicate, the apex rounded to truncate, with a J+ apical ring 1.5-2 µm diam. and ca 0.5 µm thick, usually 8-spored. Ascospores arranged uniseriately, 8-9.5 x 3.5-4 (-4.5) µm diam., ellipsoidal to fusiform-ellipsoidal, inaequilateral with one face ± flat, with an inconspicuous germ slit extending the length of the spore, mid to dark brown, fairly thick-walled, smooth, with a perispore that is dehiscent in 10% KOH.