Opegrapha reactiva  

Anamorph: not known.
Teleomorph: Ascomata appearing perithecial, in compact clusters, visible from the surface as flat or slightly sunken ± circular black spots 70-100 µm diam. on the thallus. Exciple composed of unevenly thickened hyphae 3-4 µm diam., hyaline except around the opening where they are dark olivaceous. Interascal tissue of cellular pseudoparaphyses 1.5-2.5 µm diam. Asci 55-65 x 10-12 µm, clavate, short-stalked, fissitunicate with a distinct ocular chamber, with a small cylindrical J+ ring, 8-spored. Ascospores (17.5-) 20-24 x 5-7 µm, fusiform to cylindric-ellipsoidal, 3-septate, the apices obtuse to rounded, somewhat constricted at the septa, hyaline, fairly thick-walled.