Soredia (s. soredium) are asexual reproductive structures characterized by containing both the photobiont and the mycobiont, and having no cortex. Often, they appear as a powdery or granular covering on the lichen thallus. (See also soralia.)
The white, powdery soredia of Psuedocyphellaria anomala contrast starkly with the brown thallus surface. (A. Fischer 2/2011)