Leprose thallus; powdery and granular, in shades of green. Medulla, white, diffuse, fragmentary, comprising cottony hyphae, which also intertwine with the granules of the thallus. Infertile, common

References: 
Smith, C.W. et al. editors (2009) The Lichens of Great Britain and Irelandd
Dobson, F.S. (2018) Lichens: an Illustrated Guide to the British and Irish Species