Species: Verrucaria viridula
Photos: On limestone. Teampall Chronain, the Burren, W Ireland.
Variable. Thallus usually superficial and areolate, normally pale brown but can be whitish, grey or green-grey. Sometimes +/- immersed and then appears as brown flecks on substrate. The large perithecia are half to completely immersed. Asci are 8-spored, the spores simple, 27-34(-40) x 12-22 Ám.
Chemical reactions negative.
Occurs on calcareous rocks, limestone, mudstone, mortar, brick and occasionally on soil. Common in both natural and man-made habitats.
Verrucaria viridula. April 2009