Placopsis dusenii

Placopsis dusenii is a species of lichen-forming fungus in the family Trapeliaceae. It was formally described as a new species in 1947 by Elke Mackenzie. The species epithet honours the Swedish botanist Per Karl Hjalmar Dusén, who collected the type specimen in 1896 from Desolación Island. It is a crust-forming lichen with a thick, chalky, firmly attached thallus that is distinctly areolate and lacks a marginal prothallus. The areoles are angular to irregular and fairly coarse (about 0.5–4.5 mm across), separated by deep, open cracks (roughly 0.2–1.0 mm wide) so that, under a hand lens, the thallus can look like a set of discrete "islands". Individual areoles have a characteristic minutely brain-like (cerebriform) surface texture. The upper surface is greenish white to pinkish, and the lichen lacks isidia and soredia (and is also reported without pustules or pruina). The species forms cephalodia that may be attached to the areoles or occur as discrete patches separated by cracks. They ......read more on Wikipedia.