Nemania serpens  

Anamorph: colonies ash grey, covering the young stromata and on surrounding wood. Conidiophores pale yellow-brown, smooth ca 3µm diam., branches 2-3 µm diam. Conidiogenous cells 30-50 µm long, geniculate, proliferating sympodially. Conidia 3-5 x 2-3 µm, subglobose, aseptate, pale yellow, with a small scar.
Teleomorph: stromata superficial, irregularly effuse, irregularly elliptical to elongate, at times confluent, 4-50 mm long x 2-10 mm broad x 0.5-0.8 mm thick, carbonaceous; surface dark brown to black, with conspicuous to less frequently inconspicuous perithecial mounds, when immature coated with a grey to beige hyphal layer bearing the anamorph; interperithecial tissue whitish to grey when young, disappearing, basal tissue inconspicuous; margin abrupt. Perithecia subglobose, 0.5-0.7 mm diam., the ostioles papillate, usually broadly conical, black. Asci cylindrical, long-stipitate, the spore-bearing parts 75-90 µm long x 6-8 µm broad, the stipes 60-80 µm long, with apical apparatus not blueing in Melzer's reagent, but blueing after a 5-10% KOH-pretreatment, dextrinoid (pale red brown) in Lugol's solution, inverted hat-shaped, 2.7-3.4 µm high x 2-2.7 µm broad, (4-) 8-spored. Ascospores uniseriate or biseriate, 10.5-14 x 4-5.5 µm, pale to mid olivaceous brown, aseptate, ellipsoid-inequilateral with broadly rounded ends, at times suballantoid,  with a short inconspicuous germ slit on the less convex side, sometimes with a thin non-dehiscent perispore, without appendages.

Description adapted from http://pyrenomycetes.free.fr/index.htm and Granmo et al. (1999).