Description: This is a lichen of scattered limestone fragments and pebbles. Although the thallus is hidden below the surface (endolithic), the spherical discs (perithecia), which are strengthened by a black, thickened outer shell called an involucrellum, are only shallowly immersed in pits in the rock, so can easily be seen as cone-like projections. Spores are colourless, 25–29µm and eight-spored in the ascus. The algal cells present in the discs are ellipsoid and therefore, longer (3–7.5µm) than in S. caesia. In Ireland, the species is rare.

Key Identification Features:

• Thallus endolithic; discs not deeply immersed in pits, disc with involucrellum
• Spores eight/ascus, colourless; ellipsoid, shaped like elongated bricks.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Nesothele hymenogonia at iNaturalist World Species Observations database.