1 Sporophytes present.

  2 Leaves dissected, not linear, > 20 mm wide.

    3 Sori round or oblong, distinct and separate along the pinnule margins; leaves bright-green, glabrous, herbaceous, delicate, and flexible (darker green, thicker, and hairy in A. hispidulum); [subfamily Vittarioideae]

    3 Sori continuous along the pinnule margins (or across the blade in Acrostichum); leaves mostly dark-green or glaucous, often pubescent, coriaceous, tough, and stiff (except Ceratopteris).

      4 Plant aquatic or subaquatic, pale green, delicate; [subfamily Ceratopteridoideae]

      4 Plant epipetric or terrestrial (except Acrostichum), usually dark or bluish green and coriaceous.

        5 Fertile pinnae with entire lower surface covered by sporangia; leaves 1.5-5 m long; [of wetlands, n. FL southward]; [subfamily Ceratopteridoideae]

        5 Fertile pinnae with sori marginal; leaves < 0.5 m long; [of rocky sites, collectively widespread].

          6 Leaves strongly dimorphic, the fertile leaves obviously longer than the sterile and with narrow elongate ultimate segments; [subfamily Cryptogrammoideae]

          6 Leaves essentially monomorphic.

             7 Petioles with alternating longitudinal grooves (2 or 3) and ridges on the upper surface; [subfamily Pteridoideae].

               8 Lower surface of leaf blades with white or yellow farina; sporangia along the veins, not covered by the reflexed leaf margin; [of peninsular FL in our region]

               8 Lower surface of leaf blades lacking farina; sporangia submarginal, typically covered by the reflexed leaf margin; [widespread in our region]

             7 Petioles rounded, flattened, or with a single groove on the upper surface; [subfamily Cheilanthoideae].

                 9 Leaves 1-pinnate or 1-pinnate-pinnatifid; lower leaf blade surfaces densely covered with stellate and ciliate-fringed scales; petiole with 2 vascular bundles

                 9 Leaves 1-pinnate-pinnatifid or more divided (to 5-pinnate); lower leaf blade surfaces glabrous to pubescent and/or farinose; petiole with 1 vascular bundle.

                   10 Lower leaf surface with dense white farina.

                     11 Leaf blade deltoid; white farina on lower blade surface not interspersed with shiny, dark-brown needle-like hairs; [of KY westwards]

                     11 Leaf blade lanceolate; white farina on lower blade surface interspersed with shiny, dark-brown needle-like hairs; [of s. TX only in our region]

                   10 Lower leaf surface not farinose, variously glabrous or hairy; [widespread in our region].

                       12 Leaf blade pentagonal in outline, divided into 3-5 segments which are each merely pinnatifid

                       12 Leaf blade lanceolate or ovate in outline, 1-5-pinnate.

                          13 Leaves 1-3-pinnate, the ultimate leaf-segments 8-100 mm long, glabrous or sparsely and inconspicuously hairy

                            14 Petioles slightly grooved or flattened and ultimate segments thin in texture and not strongly rolled, and also lacking a mucro or cusp at apex

                            14 Petioles either terete (not grooved/flattened), or petiole flattened, and then the ultimate segments also leathery and strongly rolled and with mucronate apex

                          13 Leaves 2-5-pinnate, the ultimate leaf-segments 1-4 (-8) mm long, more-or-less densely hairy (glabrous or glabrescent in Myriopteris alabamensis and M. microphylla).

                              15 Ultimate leaf segments cordate at the base and well-separated from one another on prominent stalks [of ec. TX only in our region]

                              15 Ultimate leaf segments never cordate, approximate to one another

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

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

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

1 Gametophytes thalloid, ribbon-like and branched.

    3 Gemmae absent or spatulate (the gemma > 1 cell wide)

1 Stem obviously jointed; leaves scale-like, borne in a whorl at each of the distant joints; spores borne in a terminal strobilus with peltate scales

1 Stem (or rhizome) not jointed; leaves scale-like or larger, but if scale-like not borne in whorls at distant joints; spores borne variously, but if in a terminal strobilus the scales not peltate.

  2 Leaves linear, grass-like, 1-60 cm long, 20× or more as long as wide.

    3 Leaves solitary (though often the internodes very short from a thin, creeping rhizome); sporangia borne in a spherical (ca. 3 mm in diameter) sporocarp on a separate branch from the rhizome

    3 Leaves numerous from a corm or short-creeping rhizome; sporangia either borne in the expanded leaf bases (Isoetes in ISOETACEAE) or in 2 rows at the tip of the linear fertile leaves (Schizaea in SCHIZAEACEAE), or in a sub-marginal groove on either side of the midrib (Vittaria in PTERIDACEAE).

      4 Leaves straight and stiff, arching, or flaccid, from a 2-3-lobed corm; sporangia borne in the expanded, hyaline leaf bases

      4 Leaves either straight and stiff or notably spiral-curly, from a short-creeping rhizome; sporangia borne in 2 rows either at the expanded pectinate tip of the fertile leaves or along much of the length of the linear leaves.

        5 Leaves 1-12 cm long, spiral-curly; plants terrestrial in peaty substrate, the leaves erect

  2 Leaves various (scale-like, awl-like, moss-like, or flat), but not linear and grass-like, mostly 1-10 (-20)× as long as wide.

          6 Leaves inconspicuous, reduced to a few nerveless scales (< 1.5 mm long), the internodes much longer than the leaves; sporangia yellowish, 3-locular, 1-2 mm in diameter; stems upright, repeatedly branched dichotomously

          6 Leaves either larger or, if scale-like, with 1 or more nerves and longer than the internodes (the leaves thus overlapping); sporangia yellowish to brownish, 1-locular, < 1 mm in diameter; stems either subterranean or surficial rhizomes or erect or ascending (and sometimes dichotomously branched in whole or in part in Huperzia in HUPERZIACEAE, and Diphasiastrum and Dendrolycopodium in LYCOPODIACEAE).

             7 Plant with leaves very numerous and overlapping along the creeping, ascending, erect, or pendant stems, the leaves scale-like or awl-like, 0.5-2 (-3) mm wide, typically acute, acuminate, or hair-tipped; sporangia either in terminal strobili (axillary to specialized, smaller leaves) or axillary to normal leaves; [Lycophytes].

               8 Sporangia borne in flattened or quadrangular strobili sessile at the tips of leafy branches; spores and sporangia each of two sizes, the megasporangia larger and borne basally in the strobili

               8 Sporangia borne either in the axils of normal foliage leaves, or in strobili sessile at the tips of leafy branches or stalked on specialized branches with fewer and smaller leaves; spores and sporangia each of one size.

                 9 Leafy stems erect or pendant, simple or dichotomously branched, the ultimate branches vertically oriented (upwards or downwards); sporophylls like the sterile leaves or only slightly reduced, in annual bands along the stem; vegetative reproduction by leafy gemmae near the stem apex (Huperzia) or lacking gemmae (Phlegmariurus)

                 9 Leafy stems prostrate or erect, if erect then generally branched, the ultimate branches spreading (horizontal) or ascending; sporophylls differing from sterile leaves, either broader and shorter, or more spreading, aggregated into terminal cones; lacking vegetative reproduction by gemmae.

             7 Plant with leaves not as above (see below for details); [Pteridophytes].

                   10 Leaves palmately lobed.

                     11 Leaves divided into separate sterile and fertile segments, the sterile leaf blade 30-90 cm long, ovate to lanceolate, entire-margined, obtuse, the longer fertile portion with 2 rows of sporangia somewhat imbedded in it

                     11 Leaves with fertile portions in patches near the tips of the lobes

                   10 Leaves unlobed (or if lobed, pinnately so).

                       12 Plant with 1 (-several) leaves, divided into separate sterile and fertile segments, the sterile leaf blade 0.3-90 cm long, ovate to lanceolate, entire-margined, unlobed, obtuse, the longer fertile portion with 2 rows of sporangia somewhat imbedded in it

                       12 Plant with many leaves, generally 5 or more, not divided into separate sterile and fertile segments, the leaves either (a) small, 0.3-1.6 cm long, obovate, scattered along a very thin creeping rhizome, or (b) larger, (2-) 8-30 cm long, cordate at base, the tip long-attenuate (often proliferous, bearing a plantlet at the tip).

                          13 Leaf blades (2-) 8-30 cm long, cordate at the base, the tip long-attenuate, often proliferous (bearing a plantlet at the tip); sporangia grouped into indusiate sori on the undersurface; leaf texture moderately thick; rhizome erect or ascending, 1.0-1.5 mm in diameter, the leaves clustered from its tip

                          13 Leaf blades 0.3-15 cm long, cuneate at the base, acute to rounded or obtuse at the tip, not proliferous; sporangia solitary in a marginal pocket on the leaf; leaf texture very thin; rhizome creeping on the surface of rock or bark, either 0.1-0.3 or 0.5-1.5 mm in diameter, the leaves scattered along it

                            14 Leaf blades 0.3-1.6 cm long; sporangia solitary in a marginal pocket on the leaves; leaf texture very thin; rhizome 0.1-0.3 mm in diameter

                            14 Leaf blades 2-15 cm long; sporangia borne in round sori on the lower surface of the leaves; leaf texture herbaceous to subcoriaceous; rhizome 0.5-1.5 mm in diameter