Lepraria

Lepraria is a genus of leprose (powdery) crustose lichens that grows on its substrate like patches of granular, caked up, mealy dust grains. Members of the genus are commonly called dust lichens. The main vegetative body (thallus) is made of patches of soredia (little balls of algae wrapped in fungus). There are no known mechanisms for sexual reproduction, yet members of the genus continue to speciate. Some species can form marginal lobes and appear squamulose. Because of the morphological simplicity of the thallus and the absence of sexual structures, the composition of lichen products (i.e., secondary metabolites made by lichens) are important characters to distinguish between similar species in Lepraria....read more on Wikipedia.