Order: Peltigerales       Family: Collemataceae Species: Lathagrium cristatum (Collema cristatum) Growth type foliose. Photos: On limestone in the Burren, Co. Clare and on wall, Foynes, Co. Limerick, Ireland. Round, semi-circular or irregular thallus, centre often disintergrating with age. Lobes thinnish, radiating, convoluted, margins wavy, entire or incised. Upper surface dark olive-green to black, lower with white tufts of hapters. Sessile or stalked apothecia with even margins, usually crowded, +/- marginal, but sometimes absent. Common throughout Ireland on hard calcareous rocks, mortar and tombstones. Chemical reactions negative.

Lathagrium cristatum (Collema cristatum). July 2009