1. Osmunda L.
Plants perennial, homosporous. Rhizomes erect to creeping, lacking hairs and
scales. Leaves variously compound, the fertile portions or fertile leaf blades
lacking vegetative tissue. Petioles with stipular flanges of tissue. Indusia
absent, the developing sporangia sometimes covered by dense, matted hairs.
Sporangia in dense clusters along the pinnule axes, splitting open vertically,
the annulus a patch of thick-walled cells on the side of the sporangium. Spores
trilete, 40–70 mm
in diameter, green, 256–512 per sporangium. Gametophytes green, flat, oval to
nearly circular.
About 10 species, nearly worldwide.