Pyrenula macrospora (Degel.) Coppins & P. James

    Thallus crustose, more or less immersed, waxy when moist, brown-greenish under rain showers, cream-yellowish to fawn when dry, minutely dotted with white pseudocyphella, 40-120 µm diam., prothallus black conspicuous notably in case of mosaics. Perithecia abundant, scattered all over the thallus without specific pattern, markedly prominent, hemispherical, ostiole central, distinctly visible, 0.5-1.2 mm diam., yielding black cupules after falling. Cylindrical asci of 140-150 x 18-20 µm according to our measurements. Elliptical spores, brown, 3-septate with a lozenge with rounded angles in each cell, 27-33 x 10-13 µm according to the literature, 27-34 x 9-12 µm according to our measurements. Pycnidia abundant, 100-180 µm diam., black, often aligned along the black prothallus line delimiting contiguous colonies, producing a characteristic 'seam line' aspect (see pictures resembling to patchworks composed of pieces of leather). Photobiont: Trentepohlia. C-, K+ yellow, KC-, Pd+/-pale yellow, UV+ yellow-orange. Rather common near the seashore on smooth bark of trees, often forming large remarkable mosaics by merging of contiguous colonies. Sometimes together with Pyrenula chlorospila of which the perithecia are smaller and ascospores with diamond-shaped locules presenting sharper angles. See  Pyrenula nitida that is K+ red-orange, has no maritime trend and has smaller ascospores.*