A foliose lichen with pale grey to greenish grey lobes that often have brownish tips. Pseudocyphellae form a coarse network of white lines and dots in the upper cortex.
The grey-brown isidia, often gathered in the centre of the thallus, stand out against the greyish or greenish grey lobes. Apothecia are infrequent, with red brown discs with thin margins that are frequently isidiate or crenulate.
Cortex: K+ yellow. Medulla: C-, K+ orange, UV-
Parmelia saxatilis is very common throughout Scotland and found on dykes and rocks, sometimes growing through bryophytes. It is found on trees occasionally. BLS distribution map
Parmelia saxatilis is distinguished from Parmelia sulcata by the presence of isidia rather than soralia. Parmelia saxatilis shares its habitat on siliceous rocks with Parmelia omphalodes, but the latter is brown and lacks isidia and soredia.
scottishlichens.co.uk 