Soralia (s. soralium) are the structures on a lichen thallus that yield soredia. They appear as an erosion of the cortex covered in granular masses.
Scanning electron micrograph of a soralium on Platismatia glauca. (A. Fischer 1/2011)
Darkfield image of the cross section of a soralium of Pseudocyphellaria anomala (~100X). (A. Fischer--3/2011)