Porina aenea (Walbr.) Zahlbr.

    Thallus crustose, thin, more or less smooth to slightly cracked, brown-greenish, greenish, brown-reddish, prothallus absent. Perithecia usually numerous, more or less immersed in the thallus, 0.1-0.3 mm diam., glossy, blackish, ostiole hardly visible. Asci 8-spored. Ascospores colourless, fusiform, one apice more pointed than the other, 3-septate, 14-20 x 4-5 µm according to the literature; 13-25 x 4-5 µm according to our measurements. Photobiont: Trentepohlia. Chemical spot tests negative. Not rare, on smooth bark of trees in humid aeas ((Acer, Fraxinus more rarely on conifers).

See Pyrenula nitida that displays brown ascospores, constricted at septum level, and above all Strigula taylorii that is very similar to the naked eyes but with pycnidia and ascospores easily subdivided when mature.