Plants short-lived, rooted or floating. Stems erect, bearing a few thin scales. Leaves dimorphic, erect to spreading, with adventitious bud initials or small plantlets along margins; proximal leaves sterile, herbaceous, venation reticulate, without included veinlets; distal leaves fertile, larger than sterile leaves; segments revolute, covering sporangia. Sporangia abaxial, thin-walled, with mixed development, bearing 0–71 indurate annulus cells. Spores yellow, 16 or 32 per sporangium, 70–150 µm diam. Gametophytes terrestrial, green, asymmetrically cordate.
Tropical, subtropical, and warm temperate regions worldwide.
Genus 1, species 3–4 (3 species in the flora).