Arthonia anglica Coppins
Thallus crustose, immersed in the bark, 5-8 cm at its greatest length, smooth, light pinkish-brown, whitish slightly tinged with pinkish-brown, delimited by a brownish prothallus. Numerous apothecia most often in very irregular stars, reddish-brown, blackish-brown. Ascospores colorless when young, brownish and rough when old, long ovoid, 3-4 times septate, with one end broader (in a club), 15-22 x 5-7 µm. Photobiont: Trentepohlia. Thallus: C-, K-, KC-, P- UV-, but an apothecia cut is C+ fleeting pink (presence of gyrophoric acid) this reaction can be observed (sometimes with difficulty!) in the field by a pink reaction fleeting around apothecia in the presence of C. Fairly rare species (but probably confused) on trees with smooth bark in woodlands and humid forests. Very similar species to Synarthonia (Arthonia) astroidestera which differs by its orange bloom under UV rays and to Arthonia stellaris which is pycnidiate and whose apothecia are not pink by C.