Rinodina roboris (Dufour ex Nyl.) Arnold var. roboris

    Thallus rather thick, continuous, uneven to markedly granular, squamulose to areolate, areoles 0.5-1 mm across, pale greyish, pale grey-greenish when dry, greenish when moist (green tinge is always distinctly visible on the thallus),  prothallus seldom visble and in that case, dark grey. Apothecia usually numerous, more or less sessile, 0.8-1.5 mm  diam., disc flat then convex, black, thalline exciple persistent, thick, wavy, irregular to crenulate, concolourous to the thallus. Ascospores ovoid, walls thick, brown-grey, 1-septate, with one rounded lumen 14-22 x 8-12 µm according to literature, 17-25 x 7-15 µm according to our measures. Photobiont: Trebouxia. C-, K+ yellow, Pd-. Common, on more or less rough barks of trees in sunny expositions. See Rinodina sophodes of which the thallus is more olive-greenish, K-, and above all with ascospores wool-ball shaped, and which grows on smoother barks. Not to be confused with Tephromela atra var. torulosa of which the thallus is less green and apothecia larger, clustered towards the center, discs flat or slightly convex, markedly black.