Synonyms: Pertusaria laevigata (Nyl.) Arnold non (Th. Fr.) Anzi; Variolaria trachythallina
Distribution: N - TAA.
Description: Thallus crustose endosubstratic to thinly episubstratic, whitish to grey, continuous, smooth or uneven, not zoned. Apothecia lecanorine, immersed in soralia-like, 0.5-1(-2) mm wide thalline warts which are constricted at base and sometimes subglobose, 1-3 per wart, with a to 2 mm wide, pink, reddish or rarely finally black, granular, white-pruinose disc. Asci (1-)2-spored. Ascospores often not well-developed, 1-celled, hyaline, ellipsoid, (38-)50-160 x 18-58 µm, the wall 5-7 µm thick. Photobiont chlorococcoid. Spot tests: thallus and/or medulla K+ yellow, C-, KC-, P+ yellow-orange. Chemistry: thamnolic acid.
Note: a cool-temperate, perhaps circumpolar lichen found on smooth bark of deciduous trees, especially Fagus, in humid montane forests. It is included as “Regionally Exctinct” in the Italian red list of epiphytic lichens (Nascimbene & al. 2013c).