Buellia schaereri is a species of lichen in the family Caliciaceae. It was formally described as a new species in 1849 by Italian botanist Giuseppe De Notaris. The botanical name honours Swiss pastor and lichenologist Ludwig Schaerer. It is a widely distributed lichen, occurring in Africa, Asia, Northern and Central Europe, Macaronesia, Central America, and North America. It grows on the bark and wood of trees, especially conifers and oak.
Buellia schaereri has a thin, effuse, pale grey thallus. It has dark brown to black apothecia that measure 0.2âÂÂ0.3 mm in diameter, with a flat to convex disc. The ascospores it makes are smooth and thin-walled with a single septum and typical dimensions of 6âÂÂ10 by 2.5âÂÂ4 üm. Pycnidia are visible as tiny (50âÂÂ70 üm) black specks on the thallus surface; they are often numerous. They produce short oblong to ellipsoid conidia measuring 2âÂÂ3 by 1âÂÂ1.4 üm.