Family: Arthoniaceae Species: Diarthonis spadicea (Arthonia spadicea) Growth type crustose Photos: Dromore, Co. Cork, SW Ireland. The thallus is thin and +/- immersed or greyish-green. Apothecia are flat or slightly convex, +/- rounded and often glossy, reddish-brown or black (and looking like tar-spots). Asci 8-spored, the spores 1-septate, 7-11 x 3-4 µm. Pycnidia frequent. Photobiont Trentepohlia. Micrographs below. Chemistry negative but apothecia and pycnidia weak K+ purple A photophobic (light-hating) species usually found near the base of shaded, basic-barked, deciduous trees in moist woodlands Similar: Arthonia didyma has smaller apothecia and larger spores

Micrographs



Diarthonis spadicea (Arthonia spadicea). August 2024