Rootstocks creeping, filiform, stipes ascending, one to three inches long, thin, very delicate, pellucid, much divided, oblong-lanceolate, bipinnatifid. Rachis narrowly winged. Sporangia clustered around the slender bristle, which is the prolongation of a vein, and surrounded by a vase-like, slightly two-lipped involucre.
On moist, dripping sandstone cliffs, Kentucky to Alabama. Often called the "Killarney fern," as it grows about the lakes of Killarney in Ireland.
[Illustration: Fruiting Pinnules of Filmy Fern (From Waters's "Ferns." Henry Holt & Co.)]
[Illustration: Ostrich Fern]
[Illustration: Cinnamon Fern]
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