Aspicilia laevata (Ach.) Arnold

      Thallus crustose, rather thin, almost smooth, continuous or slightly verrucose, delicately rimose, with few discrete areoles, often eroded according to locations, colour most often faded, varying from pale green, pale green-grey or dull yellow-greenish when dry, green when moist,  with a black hypothallus and delimiting prothallus. Apothecia more or less numerous, immersed and usually several crowded per areole, often distorted, 0.3-0.5 mm diam, discs dark-brown, flat to concave, thalline margin inconspicuous little prominent, often torn (crater or pustule like). Asci 8-spored. Ascospores broadly ellipsoid to ovoid, 13-20 x 9-13 µm. Photobiont : Chlorococcales. Thallus : C-, K+/- yellow to red, Pd+ orange. On rocks subjected to spray in or on the edges of rivers and streams. Not to be confused with  Aspicilia caesiocinerea that may extend its development to this species habitat but its thallus is much more verrucose and the apothecia almost sessiles when old and Pd-. The thallus could be mistaken for Rhizocarpon lavatum of which all the chemical spot tests are negative and ascospores different.*