Species: Phlyctis agelaea
Photos: On Acer trunk. Bantry, Co. Cork, SW Ireland.
Thin, powdery to rough, cracked thallus, whitish to pale-grey with a white prothallus. Usually fertile, with greyish, white-pruinose apothecia +/- deeply hidden in powdery-granular warts. Ascus is usually 2-spored, with muriform spores. Soralia are absent.
Thallus K+ yellow going red, C-, KC+ red, P+ orange, UV-
Infrequent but possibly overlooked on the trunks and branches of young smooth-barked trees in moist habitats. Rare on rocks.
Similar: Phlyctis argena. Thallus sorediate, apothecia rare.
Pertusaria multipuncta. Discs more exposed, thallus K+ yellow
Above: Phlyctis agelaea May 2010. Close up of apothecia