Hypoxylon fraxinophilum  

Anamorph: Nodulisporium-like. Colonies in culture slow-growing, initially white with floccose aerial mycelium, later becoming greyish brown, the reverse dark brown; when inoculated onto Corylus wood producing effuse greyish colonies with poorly developed conidiophores. Conidiophores 2-2.5 µm diam, short, unbranched or sparingly branched, conidiogenous cells not delimited. Fertile locus poorly differentiated, the apex of the conidiophores slightly swollen with restricted sympodial proliferation, producing conidia singly or in small clusters. Conidia 4.5-7.5 x 2.5-4 µm, ovoid to ovoid-ellipsoidal, hyaline, aseptate, smooth-walled, without a gelatinous sheath or appendages.
Teleomorph: stromata erumpent from the surface layers of bark, 2-6 mm diam and 1.5-2.5 mm tall, ± hemispherical, somewhat constricted at the base, pinkish brown to grey-brown, with yellow or yellow-green pigments extractable in KOH, the internal tissue below the ascomata dark grey-brown when mature. Ascomata in a single layer, somewhat raising the stroma surface and with conspicuous slightly sunken ostioles surrounded by a raised white ring of unpigmented tissue; 350-450 µm diam and 400-650 µm tall, ± globose to obovoid but sometimes irregular in shape due to compression, the walls black. Interascal tissue of simple persistent thin-walled hyaline paraphyses 2.5-3 µm diam, not swollen at the apex. Asci 170-220 x 14.5-17 µm, cylindrical, long-stalked (to 120 µm in length), fairly thin-walled and without discernible wall layers, the apex obtuse, sometimes with an inconspicuous J- apical ring, 8-spored. Ascospores arranged obliquely uniseriately, (17.2-)18-23(-24.1) [mean=20.1, sd=1.9, n=29) x 9.2-11.6 (mean=10.4, sd=0.75, n=13) x 10-12.8 (mean=11.1, sd=0.77, n=17) µm, ellipsoidal-fusiform and strongly asymmetrical with one face often ± flat or slightly concave, the ends obtuse, dark chestnut-brown, with a ± straight germ slit extending the entire length of the spore on the opposite face to the flattened one; aseptate, thick-walled, with a perispore with inconspicuous helical ornamentation that dehisces in KOH, without a gelatinous sheath or appendages.