Chrysothrix granulosa

Chrysothrix granulosa (Coastal gold dust lichen) is a brilliant yellow, powdery (leprose) lichen that grows in irregular patches mostly on bark (sometimes wood and rock) in shaded dry areas of coastal western North America and western South America.[1]^:253–4[2]

In North America it is found from Mexico to as far north as British Columbia.[1] It can be found in coastal areas of California[1] near Santa Barbara County,[2] and coastal areas of the Sonoran Desert, mostly islands off Baja California.[2] In South America it is found from Chile to Peru.[2] It is found at elevations from sea-level to 400 metres (1,300 ft).[2]

The mostly structureless body (thallus) forms powdery cushions of lichen granules (soredia) over a fluffy middle layer (medulla).[1] The upper medulla is yellow fading to yellow-white in the lower part.[2] It lacks fruiting bodies (apothecia).[1] Fruiting bodies (apothecia are absent in populations in California and the Sonoran Desert, and elsewhere have a constricted base with 0.2 to 1 mm diameter brownish orange flat to convex discs.[2]

Lichen spot tests are K+ orange, C-, KC-, and P+ orange, with UV+ a dullish dark orange.[1] Secondary metabolites include calycin acid and diffractaic acid.[1]