Description: There are several inconspicuous, scurfy-bodied crusts which grow on limestone. Psorotichia schaereri is one such species that lingers in the shade. The granular-squamulose thallus is easily overlooked for Placynthium nigrum but the reddish, brown-black discs (0.2-0.6mm diam.) clearly mark it out as something different. The granules can be minutely isidiate so require close inspection. The spores are simple and ellipsoid usually within the range 14-18&

371;m long. Confined to shaded limestones where there may be some seepage or permanent dampness. Western Ireland.

Key Identification Features:

• Small scurfy crust of minute, brownish granular-isidiate squamules (<1mm long); on shaded, mostly horizontal limestones — sometimes along seepage tracks
• Discs reddish and convex when mature (like red ‘Fruit Pastilles’ not black as in Placynthium).

Original text submitted by Vince J. Giavarini

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

iNaturalist: Collemopsis schaereri at iNaturalist World Species Observations database.