A foliose species with a characteristic bluish grey colour. The lobes tend to be arranged in rosettes, are strongly adpressed and have numerous minutes pale pseudocypehellae. It is identified by the globular masses of blue-grey soralia.
Cortex and medulla: K+ yellow
In Scotland, Physcia caesia is common in lowland and coastal areas where it is found on nutrient-rich basic rocks, including gravestones, as well as dust-impregnated timberwork like fenceposts. BLS distribution map
Physcia caesia is distinguished from Physcia dubia on basis of the presence of globular masses of blue-grey soralia that are laminal and a preference for basic substrata.
scottishlichens.co.uk 