Order: Lecanorales       Family: Rhizocarpaceae Species: Rhizocarpon reductum Growth type crustose. Photos: Co. Cork, SW Ireland. Specimen left identified by J. Douglass Cracked-areolate, greyish to mousey-brown thallus with thin black prothallus. Black apothecia with thin, persistent margin, initially innate, becoming sessile. Dark green to greyish-brown epithecium. Asci 8-spored, spores muriform with 8-13 cells, 20-35 x 10-15 µm, colourless. Microscope photographs below. A pioneer species of siliceous rock, pebbles and tombstones. Chemical reactions variable, usually K+ yellow, C-, P+ orange. Rarely K-, P- or K+ red, P+ orange. Similar: Rhizocarpon lavatum. Chemical reactions negative.

Microscope photographs



Rhizocarpon reductum