Caliciaceae Buellia subdisciformis Growth type crustose Chemical results: K+ yellow > red, C-, P+ yellow-orange, UV- Usually coastal on hard, siliceous rocks and can be locally abundant on south-west and western coasts, forming large colonies The white or pale grey, areolate thallus can be thin or thick and is often surrounded by a black prothallus. Apothecia are flat or slightly convex, the discs black and discs and margins initially white-pruinose. Asci 8-spored, the spores greenish-brown, 1-septate, 9.5-19.5 x 5.5-10 µm. Similar: Buellia ocellata. Thallus yellowish. K-, C+ persistent orange, P-

Buellia subdisciformis
On chert, Portland, Dorset. February 2016