Sulphur Dust Lichen

Psilolechia lucida forms a sulphur-yellow to yellowish green crust, although the colour is greener when the surface is wet. The crust comprises powdery soredia that can be thin or thick, and sometimes divided into irregular areoles. The apothecia (typically less than 0.3 mm in diameter) are yellow, ranging in shape from hemispherical to irregular and lumpy, and lack margins. The ascospores, which number eight per ascus, measure 4–7 by 1–2.5 μm.

This is a widespread species that is found throughout the world. It is common and widely distributed in Europe. In Asia, Psilolechia lucida has been reported from Japan; from the Middle East is found in Turkey; from Africa, it is known from the Canary Islands, and Madeira. In South America, it has only been reported from Bolivia and Chile. It has also been found in Oceania, Central America, and the Antarctic Peninsula. It grows on rocks, both calcareous and siliceous, as well as artificial rocky substrates such as bricks and concrete. The lichen grows in the shade, and is often found growing in sheltered underhangs. Rarely, it is found growing on hardwood tree bark, at the base of the tree or on the roots above ground.