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, pale brownish, parfois teinté de pourpre autour des apothécies dans la viellesse, delimited by a brownish hypothallus. Apothecia numerous, not pruinose, most often in very irregular stars, reddish-brown, blackish-brown, blackish, often with a projecting border formed by an outgrowth of the thallus. Ascospores colorless if young, brownish and rough if old, long ovoid, 3-4 times septate, with one end wider (club-shaped or ice-cream cone), 15-22 x 5-7 µm according to the literature, 15- 25 x 7-9 µm according to our measurements. 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 the apothecia in the presence of C but more persistent with KC (in the form of a reddish halo around the apothecia). Quite rare oceanic species (but probably confused) found on smooth-barked trees in woodlands and humid forests.

Easy to confuse (and probably confused!) with:

Synarthonia (Arthonia) astroidestera  which differs by its orange bloom under UV rays and C-;

Arthonia radiata whose apothecia are not C+ pink and whose spores do not have an enlarged apex.

Coniocarpon cuspidans whose apothecia are reddish and K+ red.