Arthoniaceae Arthonia vinosa Growth type crustose Thallus K+/- pale purple, C-, Pd-, UV-. Apothecia K+ purple Occurs on bark or lignum of (usually) Quercus and Alnus in old woodland Thallus immersed or scurfy, whitish to pale fawn and often stained yellowish-orange. Rounded orange-brown to brownish-black apothecia, in section yellow-orange or brown-red. Spores colourless, 1-septate, 11-15 × 4-5 µm, brown and warted when old. Pycnidia frequent. Micro photo below. Similar: Arthonia spadicea, smaller spores, pigment not dissolving in K

Microscope photograph

Arthonia vinosa
Arne, Dorset. February 2014