Parmeliaceae Parmelia saxatilis Chemical results: Medulla K+ orange turning red, C-, P+ orange, UV- Very common on walls and rocks, also found on acid barked trees. Thallus is blue-grey to green-grey with ridged lobes, the tips often browned, and covered by conspicuous white pseudocyphellae. Grey-brown isidia form on the reticulations and can spread to cover thallus. Underside with simple rhizines. Apothecia infrequent, reddish-brown with thin margins. Similar: Parmelia sulcata is sorediate, isidia are absent. Parmelia ernstiae has pruinose lobes, folioles usually present Lichenicolous fungi on Parmelia's include Marchandiomyces corallinus, Abrothallus parmeliarum and Homostegia piggotii

Parmelia saxatilis
On Birch. Canford Cliffs, Dorset. March 2013