Species: Verrucaria nigrescens
Photos: On churchyard memorial. Macroom, Cork, SW Ireland.
Dark brown to blackish thallus regularly cracked into +/- smooth areoles, occasionally with blastidiate margins. Perithecia half to three-quarters immersed. Prothallus inconspicuous or absent.
Very common throughout Ireland on calcareous rocks, walls and mortar, rare on acidic rocks. Chemical reactions negative.
Verrucaria nigrescens. Protestant churchyard, Macroom, Co.Cork. December 2008