Hypoxylon fragiforme  

Anamorph hazel brown, velvety, covering young stromata in early stages. Conidiophores hyaline to slightly pigmented, roughened, Nodulisporium-like. Conidiogenous cells 15-27 x 3.3.5 µm. Conidia ellipsoidal to nearly globose, 4-4.8 x 3.5-4 µm, hyaline or pale yellow, aseptate, thin-walled.
Teleomorph: stromata hemispherical to nearly spherical, frequently with conspicuous perithecial mounds, 2-9 mm diam. and 1.5-7 mm high; surface rust to bay-brown, with orange-red granules beneath surface yielding orange KOH-extractable pigments , in early stages with a conspicuous layer of white granules under the surface in which perithecia develop, later with a variably thick, almost black layer above the perithecia with orange pigment below; the tissue below the perithecial layer black, massive, up to 6mm thick, extending upwards between the perithecia when aged. Perithecia obovoid, 250-380 µm diam. and 450-650 µm high, quite long-necked. Ostioles lower than or at the same level as the stromatal surface, black. Asci 135-180 µm total length x 7-10 µm broad, the spore bearing-parts 64-92 µm long, the stipes 60-96 µm long, with apical ring amyloid, discoid, 1-1.3 µm high x 2.5-2.8 µm broad,  8-spored. Ascospores dark brown, ellipsoid-inequilateral, frequently crescent-shaped, 10-15 x 4.8-6.8 µm, with germ slit spore-length on the convex surface; perispore dehiscent in 10% KOH, smooth.

Description adapted from http://pyrenomycetes.free.fr/index.htm