English: A lichen - Pertusaria pertusa. Many lichens produce spores in clearly visible disc-shaped structures; however, this particular species has a distinctive and unusual appearance, because the discs, though still present, are usually apparent only as little dark pits set into wart-like structures, as can be seen in this photograph. There are often several pits per wart, making the surface seem encrusted with tiny irregular dice.

This particular example was growing on the bark of a tree that was standing alongside a footpath in an area of broad-leaved woodland.

See also 1221559.

For other Pertusaria species, see 987855 and 1050177.