Identification: Thallus pale grey to grey green often with brownish tips. Lobes to 3mm wide, widening slightly at the tips, covered in a network
of raised white lines and dots ( pseudocyphellae ). Isidia with grey brown tips are formed along the lines and spread across the upper surface. Lower surface black, lighter at the margins with simple or rarely bottle brush rhizines . Apothecia infrequent, up to 1cm diameter. Disc dark red brown with margins frequently isidiate or crenulate.
Chemistry: Cortex K+ yellow, Medulla K+ orange turning red, P+ orange, UV
Similar species: Distinguished from Parmelia sulcata by having isidia rather than soralia
Habitat: Common on trees, stone walls and rocks.
Distribution: Throughout Britain and Ireland
Photo: Mike Sutcliffe. Text: David Brabban
