Pyrenula macrospora  

Thallus crustose, olivaceous, or fawn to dark brown, immersed in bark and sometimes inconspicuous, often with black zone lines between colonies, pseudocyphellae present, 40-120 μm diam., white. Isidia and soralia absent. Photobiont Trentepohlia.
Anamorph: conidiomata pycnidia, visible as dark dots 100-180 μm diam., frequent, mostly in young parts of thallus, often clustered along junctions between adjacent thalli. Conidia 10-16 × ca 0.8 μm, narrowly falcate.
Teleomorph: ascomata perithecia, (0.4-) 0.5-0.9 (-1.2) mm diam., forming convex to hemisphaerical projections, immersed, black, often with conspicuous central crateriform ostioles. Involucrellum developed around and not clearly distinct from the peridium, composed of filamentous hyphae interspersed with bark cells and colourless calcium oxalate crystals. Peridium also containing numerous calcium oxalate crystals. Hymenium not containing anthraquinones. Interascal tissue at first of branched and anastomosed, sparsely septate periphysoids, ± unbranched paraphyses developing later and replacing the periphysoids, within a gelatinous matrix. Asci cylindrical to cylindric-clavate, short- to long-stalked, the apex obtuse and sometimes slightly attenuated, fissitunicate with rostrate dehiscence, not staining in iodine, 8-spored. Ascospores arranged obliquely uniseriately to biseriately, (24-) 27-33 (-36) × (8-) 10-13 μm, ellipsoidal to cylindric-ellipsoidal, with three conspicuous distosepta, the lumina angular to ± globose, pale to mid brown, the wall smooth or sometimes with inconspicuous striations, without an epispore or gelatinous sheath or appendages.
Chemistry: thallus C–, K+ yellow, KC–, Pd+ faintly yellow, UV± weak yellow (unidentified substance).