1 Gametophytes only present, not in association with or in close proximity to filmy-fern sporophytes.

..2 Gametophytes thalloid, ribbonlike, flattened

..2 Gametophytes filamentous in part or in whole, forming felt-like mats.

....3 Gametophytes strictly filamentous; [of inland physiographic provinces, on ceilings and back walls of rock grottos]

....3 Gametophytes filamentous and also bearing flattened blades tipped by gemmae; [of rotting wood in the Coastal Plain]

1 Sporophytes present.

......4 Leaves simple to slightly lobed, < 2 cm long; rhizomes filiform, <0.5 mm in diameter.

........5 Leaves glabrous or with simple hairs; rhizomes densely covered with dark-colored hairs

........5 Leaves stellate pubescent; rhizomes glabrous or with sparse light-colored hairs

......4 Leaves pinnatifid to pinnate-pinnatifid, > 2.5 cm long; rhizomes filiform or moderately stout.

..........6 Rhizomes erect, the leaves clustered at the tip; leaves 1-pinnatifid; [of rotting wood in the Coastal Plain]

..........6 Rhizomes long-creeping, the leaves scattered along the rhizome; leaves 1-pinnatifid to 1-2 pinnate-pinnatifid; [of inland physiographic provinces, of moist rock].

............ 7 Leaves with dark stellate hairs in the lobe sinuses; [of Coastal Plain of s. FL]

............ 7 Leaves lacking stellate hairs; [of inland provinces, rarely Coastal Plain of AL and MS].

............ ..8 Rhizomes filiform, < 0.5 mm in diameter, glabrous or with sparse light-colored hairs; indusium ("involucre") bivalvate (deeply divided into 2 flaps); receptacle not exserted from between the deeply bilobed indusium; margins of finest leaf divisions with sharp teeth pointing towards the division apex (at 20× magnification)

............ ..8 Rhizomes moderately stout, 0.8-1.5 mm in diameter, densely clad with dark-colored hairs; indusium ("involucre") tubular or funnelform, sometimes slightly 2-lobed; receptacle long and whiplike, exserted from the mouth of the tubular (slightly bilobed) indusium; margins of finest leaf divisions entire or with obscure crenations (at 20× magnification)