Stereocaulon pileatum Ach.Primary thallus crustose, persistent, greyish-white, composed of scattered, verruciform to more or less coralloid, up to 3 mm wide warts with white apices; secondary thallus fruticose. Pseudopodetia firmly attached, short, (2-)3-5 mm tall, generally simple, with a terminal globose soralium, sometimes with scattered, greyish-white, mostly granular, rarely cylindrical phyllocladia. Cephalodia small, flattened, verrucose, greyish-brown, often with a violet tinge, located amongst basal warts and on pseudopodetia, with <i>Stigonema</i>. Apothecia very rare, with a red-brown disc. Proper exciple brown in outer part, colourless within; epithecium yellow-brown, K-; hymenium colourless, 50-65 µm high; paraphyses mostly simple, 1.5 µm thick at mid-level, the apical cells to 3 µm wide, with a dark cap; hypothecium colourless or yellowish grey. Asci 8-spored, cylindrical-clavate, with a K/I+ blue outer layer and apical dome, and a central, K/I+ darker blue tube, <i>Porpidia</i>-type. Ascospores 3-septate, hyaline, fusiform, wider at one end, 20-30 x 4-5 µm. Pycnidia rare. Conidia 1-celled, hyaline, cylindrical, straight or slightly curved, 6-8 x 1 µm. Main photobiont chlorococcoid. Spot tests: K+ yellow, C-, KC+ violet (reaction often difficult to observe macroscopically, best evident on acetone extract on filter paper!), P- or P+ slowly pale yellow, UV- or UV+ blue-white. Chemistry: atranorin and variable amounts of lobaric acid.