Athallia cerinella

Athallia cerinella is a species of bark-dwelling lichen in the family Teloschistaceae. It has a thin, pale grey thallus that is often almost invisible, with small, crowded, pale yellow to orange apothecia (fruiting bodies) typically less than 0.4 mm across. The species grows mainly on the bark of deciduous trees such as ash, elder, and poplar, often on twigs and small branches in nutrient-enriched habitats. It is widespread across Europe and has also been reported from the Americas and Australasia. In the field it is virtually indistinguishable from the similar Athallia cerinelloides, but differs microscopically in having 12–16 ascospores per ascus rather than eight....read more on Wikipedia.