Description: This lichen produces its spherical discs (perithecia) in pits in hard limestone which therefore need to be dug out with the tip of a probe or razorblade before examining under the microscope. S. caesia has discs with eight-spored asci when fully developed. The spores are colourless, 35–45µm long. It is important to note the appearance of the algae within the disc which, in this species, are very slightly longer than they are wide; on well-lit limestone. In west Ireland mainly.

Key Identification Features:

• Thallus endolithic (out of sight – buried in the thallus); discs in deep pits
• Discs with eight-spored asci and colourless spores; algae shaped like slightly elongated cubes or short bricks (3–5µm); well-illuminated limestone.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Staurothele caesia at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Staurothele caesia at iNaturalist World Species Observations database.