MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
Tar lichen (Verrucaria maura) is a lichen that forms a thin, matt-black layer on rock surfaces just above high tide that can resemble an oil stain. Reproductive bodies may be present as tiny black spots. Under magnification the surface is seen to be covered with a mesh of fine cracks that resemble dried mud. The shore line is an island off the coast of North Brittany, France.
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