Order: Arthoniales       Family: Roccellaceae Species: Schismatomma decolorans Growth type crustose. Photos: On Oak trunk. Macroom, Co. Cork, SW Ireland. Identification confirmed by B. Coppins Thin whitish, lilac-grey or pinkish-grey thallus, scratching yellow-orange. Often with a grey-black prothallus. Punctiform mauve-grey soralia spread to +/- cover thallus giving leprose appearance. Apothecia and pycnidia are rare. Can be abundant on bark on the dry side of young and mature trees. Tolerates relatively high levels of agricultural fertilizers and chemicals. Chemical reactions negative. Similar: Arthonia pruinata, C+ red, usually fertile. Enterographa sorediata, waxier thallus, paler soralia. P+ rust-red

Schismatomma decolorans February 2010