Description: To the naked eye there is nothing to distinguish this black, felty, filamentous lichen from Cystocoleus ebeneus (described elsewhere). It grows in sheltered crevices and shaded underhangs of upland, acid rocks where it associates with species of Micarea, powder lichens (Lepraria sp.) and Cystocoleus. Under the microscope it differs in the configuration of the fungal threads (hyphae) which grow parallel to the algal filaments. By contrast, those in Cystocoleus are lumpy and higgledy-piggledy. Discs are absent from all filamentous lichens. Patchy distribution in Ireland; probably under-recorded.

Key Identification Features:

• Felt-like texture resembling shreds of loft insulation but black
• Under the microscope the fungal hyphae form parallel stripes across the cells.

Original text submitted by Vince J. Giavarini

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

iNaturalist: Racodium rupestre at iNaturalist World Species Observations database.