1. Adiantum L. (maidenhair fern)

Rhizomes short-creeping (long-creeping elsewhere). Leaves 1–2 times compound, glabrous (to 4 times compound, hairy elsewhere). Pinnules obliquely wedge-shaped to nearly rectangular, lobed apically. Veins easily seen, branching dichotomously 1 to several times. Sori on the underside of the recurved margins of the pinnules. Spores 64 per sporangium, 20–50 mm in diameter, yellow to light brown. About 200 species, worldwide.

Several species of maidenhair ferns are cultivated either as indoor plants in homes and greenhouses or as garden plants outdoors. The character of sporangia borne on the undersurface of the reflexed margins of the pinnule lobes, rather than on the main surface of the pinnule and covered by the reflexed margins, makes this genus easily recognizable when plants are fertile.