Description: This is one of the commonest crustose lichens of upland acid streams as it forms extensive mosaics on outcrops and boulders easily visible from a distance. The grey to creamy-yellow thallus is dotted with flat, black discs (up to 1.5mm diam.) with a thick margin thus making it conspicuous; this is especially important when growing next to related species of Rhizocarpon. During spate conditions when spray is flung about, road bridges with hard, acid rock capstones can become colonised. Spores muriform, 30-40 x 14-18&

371;m. Throughout Ireland.

Key Identification Features:

• Grey to cream-yellow thallus; black discs with thick margin and large muriform spores
• On siliceous bedrock and boulders: streams, rivers and lough edges.

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Rhizocarpon lavatum at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Rhizocarpon lavatum at iNaturalist World Species Observations database.