The maidenhair spleenwort (Asplenium trichomanes) belongs to Aspleniaceae (the Spleenworts family). It is an evergreen fern that is distributed to Miyagi Prefecture of Honshu, south to Shikoku and Kyushu, and widely temperate regions around the world. This fern grows on rocks in the mountains and on stone walls in Satoyama areas where farmland meets the forest. The petiole is purplish brown and shiny, shorter than the leaf blade. The leaf blade is a linear lanceolate, single winged compound leaf, 15 to 25 cm in length, and has about 20 pairs of slanted ovate or fan-shaped elliptic pinnae. There are 6 to 8 sori (sporangia) on each pinna.