Rhizocarpaceae Rhizocarpon richardii Growth type crustose Chemical results: Medulla: K+/- yellow, usually C+ red, P+/- orange. Usually coastal, found on siliceous pebbles, rocks and stable shingle. Brown to greyish-brown, areolate-cracked thallus, often with purplish tinge. Fimbriate blackish-brown prothallus is often present. Innate, flattish black apothecia with thin margins. Spores 22-27 x 11-14 µm, mainly 1-septate, but secondary septa sometimes occur. Epithecium K-, dark-green or grey. Similar: Rhizocarpon hochstetteri and Rhizocarpon reductum are C-

Rhizocarpon richardii
On chert, Portland, Dorset. February 2016