Teloschistaceae Pyrenodesmia alociza (Caloplaca alociza) Growth type crustose Chemical results: Apothecia K-, epithecium K+ mauve-lilac Usually in unpolluted coastal areas on hard, sunny limestone rocks Thallus immersed and inconspicuous or sometimes appearing like a thin, scurfy grey film. Black prothallus often present. Numerous blackish apothecia, sometimes with a whitish-grey pruina, are sunk in the rock and leave shallow pits. Spores 1-septate, 15-18 x 7-8 µm, septum 1-3 µm wide. Similar: Pyrenodesmia chalybaea has a thicker thallus and immersed apothecia. Could also be confused with Rinodina bischoffii

Pyrenodesmia alociza (Caloplaca alociza)
On limestone. Portland, Dorset. March 2016