Pyrenula nitida (Weigel) Ach.

    Thallus crustose, more or less immersed in the bark, smooth, bright, olive-green, greenish, brown-greenish when moist, pale brownish and 'bread-crust', beige, pale ochre, yellow-ochre when dry; withish (snow sky-like) pseudocyphella scattered, although sometimes rare. Perithecia numerous, equally distributed over the thallus, hemispherical to broadly conical, without involucrellum, 0.6-0.8 mm diam., black, hymenium with a brown-orange pigment becoming K+ brighter. Asci 100-130 x 10-15 µm according to our measurements, with 8 spores. Ascospores brown, narrowly ellipsoid, sometimes slightly bumpy, 3-septate, delimiting 4 polygonal locules, 19-24 x 6-8 µm according to the literature, 20-25 x 6-8 (9) according to our measurements. Photobiont: Trentepohlia. Thallus : C-, K+ red-orange notably around perithecia, Pd-. Rare in our prospection area owing to its continental trends (and not maritime), on smooth bark of deciduous trees (Fagus, Carpinus, etc.). N.B. On the field rather difficult to distinguish from Pyrenula macrospora that is K+ yellow and Pd+/- yellow and has larger perithecia and ascospores.