The Wart Fern

The leaves of Microsorum punctatum, more commonly known as the Wart Fern, are covered in raised, wart-like structures known as sori. These sori are spore-producing structures characteristic of ferns. In the wart fern, the sori are actually located on the underside of the leaf, but are sunken so deep that they form wart-like protrusions on the upper leaf surface.