Pyrenula oleosa

A lichen characteristic of tropical regions, widespread throughout the Caribbean, growing on tree bark, with a crustose whitish thallus showing cream or greenish tinges, and minute subglobose to globose perithecia immersed in the thallus, only 0.2 to 0.4 mm in diameter, black and carbonaceous in appearance.

Symbiotic algae belonging to the genus Trentepohlia, globose to elongated, linked in short chains.

Asci clavate to cylindrical-clavate, bitunicate, eight-spored, 115 to 150 µm long, 30 to 45 µm wide, with spores arranged biseriately to slightly overlapping inside the ascus, with a well-defined apical ocular chamber, and without any reaction in Melzer's reagent (inamyloid).

Paraphyses abundant, filiform, very slender, only 1 to 1.5 µm wide, simple or very sparsely branched, hyaline and without apical enlargements.

Ascospores ellipsoidal to fusiform, with numerous longitudinal and transverse septa (muriform), pale brown to dark brown with maturity, 35 to 50 µm long, 13 to 20 µm wide, containing numerous oil droplets (guttules) inside.