Description: This is a lichen of tree bole mosses and tree bole crevices in humid districts of western Ireland. B. marginatum has a greenish-white, thinly-powdery thallus. Discs (0.3-0.7mm diam.) are brown to black, often with a bluish tinge and with a prominent, raised, non-woolly edge (exciple). The spores are three-septate. In Ireland, there are a few records from the north.

Key Identification Features:

• Discs without ‘woolly’ exciple; with a slight bluish tinge; spores three-septate
• Low down on tree bole crevices spreading to mosses; humid woods.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Byssoloma marginatum at iNaturalist World Species Observations database.