Physcia tribacia (Ach.) Nyl.
Nylander, Flora 57: 307: 1874
Basionym: Lecanora tribacia Acharius, Lich. Univ.: 415. 1810
Foliose, orbicular to irregular, up to 3 cm diam.
Up to 1 mm wide, sometimes scale-like; margin: mostly crenulate when soralia not present, eciliate
Whitish gray to dark gray or cream-colored (with darker margins), shiny and epruinose or rarely weakly pruinose, sorediate
In marginal or terminal soralia that develop from the lower surface of the lobe tips, eroding the tip and sometimes also the lower surface
Lower Side :
White to brownish gray, often weakly rose colored
Upper cortex: paraplectenchymatous with rounded cells, medulla: white, lower cortex: paraplectenchymatous with rounded cells
Uncommon, up to 2 mm diam.; margins: partly sorediate; disc: dark brown to black, without pruina
Brown, 1-septate, intermediate between Physcia- and Pachysporaria-types, (16-) 17.5-21.5 (-22.5) x (7.5-) 8.5-10.5 (-12) µm Pycnidia: usually numerous conidia: subcylindrical, 4-6 x 1 µm
Cortex K+ yellow, C-, KC-, P+ yellow; medulla K-, C-, KC-, P- Secondary metabolite: upper cortex with atranorin