Order: Peltigerales Family: Collemataceae
Species: Collema crispum
Photos: On walls. Co. Waterford and Co. Cork, Ireland.
Wet specimen below identified by John Douglass.
Small thallus of greenish-brown to black overlapping lobes, slightly swollen when moist. Lobe margins +/- ascending, wavy, entire or crenate, never swollen. Centre of thallus with globular isidia that become flattened and squamulose, resembling small lobes. The flat apothecia are infrequent, often with lobules on margins. Microscope photographs below.
Common throughout Ireland on damp, calcareous substrates; walls, crumbling mortar, rocks. Chemical reactions negative.