Porinaceae Porina chlorotica Growth type crustose Chemical results negative. Involucrellum K- or K+ grey-brown Most frequent on damp, shaded, siliceous rocks, rare on bricks. Occasional on smooth bark where it can be confused with Porina aenea A thin dull brown, greenish or blackish thallus (which never appears oily). Small perithecia (to 0.3mm), involucrellum purplish brown. Spores 3-septate, (12.5-)14.5-18(-32) × 3.5-4.5(-6) µm. Micro photograph below. Similar: P. byssophila. Involucrellum K+ bluish-grey, spores 3(-7) septate

Microscope photograph

Porina chlorotica
Church Knowle and Canford Magna, Dorset. March 2014, February 2016