Cystocoleus is a fungal genus in the family Cystocoleaceae. The genus was established in 1849 by the British botanist G.H.K. Thwaites and is now considered to contain only one species, Cystocoleus ebeneus. These fungi form minute, sooty-brown to black patches made up of densely packed, brittle filaments that have a fluffy, felt-like appearance. They typically grow on shaded rock faces or damp bark near running water.

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