Order: Gyalectales Family: Coenogoniaceae
Species: Dimerella luteaGrowth type crustose.
Photos: On shaded Willow. The Gearagh, Co. Cork, SW Ireland.
Thallus thin or evanescent, light greenish-grey. Apothecia yellow-orange with paler margins, can appear +/- translucent in very wet conditions, possibly seasonal. Pycnidia are occasional, pale yellow. Ascus 8-spored. Spores colourless, 1-septate, 8-11 x 2.5-3.5 Ám. Microscope photographs below.
Chemical reactions negative.
Occurs on moss and bark on deciduous trees in shady, damp old woodland.
Similar: Dimerella pineti has smaller pinkish-white apothecia.
Caloplaca species are K+ red.