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Thelypteridaceae A family of leptosporangiate ferns with the mixed type of sorus. The sori are superficial, small, near the pinnule margins, and have either no indusium or a kidney-shaped one that is soon evanescent. The leaves are normally bipinnate and hairy; scales on the frond stalk or stipe are few. Thelypteris thelypteroides (marsh fern) is the most familiar European and temperate N. American species; it has creeping rhizomes and grows in fen peat. The family is now regarded as containing some 30 genera and 900 species, mostly tropical.