Irish lichens

Verrucaria nigrescens
Order: Verrucariales       Family: Verrucariaceae

Species: Verrucaria nigrescens

Growth type crustose.
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. Asci are double-walled, 8-spored, spores 17-28 x 8-14 Ám.

Very common throughout Ireland on calcareous rocks, walls and mortar, rare on acidic rocks. Chemical reactions negative.

Similar: Verrucaria nigrescens f. tectorum develops green or olive-brown blastidia on the surface of the aureoles

Verrucaria nigrescens       Verrucaria nigrescens

Verrucaria nigrescens
Verrucaria nigrescens. Protestant churchyard, Macroom, Co.Cork. December 2008

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