Chaenotheca furfuracea (L.) Tibell
Thallus leprose to granular, bright and vivid yellow-sulfur, yellow-lemon. Apothecia globose or subconical, 1,5-2,5 mm diam., blackish but appearing greenish due to a yellow-greenish pruina, developing at the tip of a 2-3 mm high spindly stalk. Ascospores brown, globose, 2,5-3 µm diam. Photobiont : Schistococcus. Chemical spot tests negative. Species often undetected in spite of the bright colour of its thallus, in wet crevices and in shaded situations on bark of trees (notably conifers) or more seldom on rocks. N.B. The sterile thallus can easily be confused with Psilolechia lucida. See Chaenotheca chrysocephala of which apothecia are smaller, ascospores bigger and, above all, photobiont is a Trebouxia.