Hypoxylon petriniae

A species characterized by the reddish-orange KOH-extractable pigments of its stromata.

Asci cylindrical, 8-spored, uniseriate, up to 150 µm long and 7-10 µm wide, with all spores concentrated in the upper half of the ascus, with a marked amyloid apical disc in Melzer's reagent.

Interascal paraphysis-like elements filiform, hyaline, septate, only 2-3.5 µm wide.

Ascospores ellipsoidal, flattened on one side, smooth-walled, dark brown under the microscope, with a straight to slightly sigmoid germ slit extending almost the entire spore length, and a perispore dehiscent in KOH.