Bacidina adastra

Bacidina adastra is a species of corticolous (bark-dwelling) leprose lichen in the family Ramalinaceae. The lichen has a distinctive thick, powdery, bright yellowish-green thallus, forming patches up to half a metre in diameter. First described in 2003 from the Netherlands, it has since been documented throughout Western and Eastern Europe in countries including Belgium, England, Germany, Poland, Russia, and Sweden. The lichen primarily grows on tree bark, especially on nutrient-enriched bases of trees like poplar, willow, and elm, though it can occasionally be found on wood, soil, and rock. Its fruiting bodies (apothecia) appear rarely and vary in colour from pale pink to dark blue-black. The species is sometimes confused with free-living green algae or similar lichens, particularly Bacidina neosquamulosa, but can be distinguished by its granular growth pattern and microscopic features....read more on Wikipedia.