Northern Maidenhair fern, a native species, has been added to the USWildflowers database (09/16/2010.)  Scientific name is Adiantum pedatum.  Another common name is Five-Fingered Maidenhair Fern.  Photo below was taken on Big Frog Mountain in Polk County, TN on May 2, 2010.

Northern Maidenhair, Five-Fingered Maidenhair Fern - Adiantum pedatum