Plants usually small, terrestrial. Rhizomes short-creeping, decumbent to erect, covered with hairs. Fronds small, simple, dimorphic, sterile fronds grasslike, fertile fronds with diminutive blades at tips. Blades fistlike clusters of small pinnae. Sporangia on abaxial surfaces of pinnae
under revolute margins.

A genus of about thirty species from mostly tropical and south-temperate areas, but also including one rare species found in the northeastern United States. Represented in Hawai'i by a single endemic species.