Porpidiaceae Porpidea macrocarpa Growth type crustose Chemistry: Medulla and apothecia margin: K+/- yellow, P+/- orange Common on siliceous rocks and large boulders, most frequent in upland areas. Very variable. Thallus either thin or +/- cracked and warted, grey, greenish or sometimes stained rust-red in places from oxidation. Abundant large apothecia (to 3mm diam), black with thick, often contorted margins. Similar: Porpidia platycarpoides

Porpidea macrocarpa
On ironstone. Brands Bay, Dorset. May 2013