ARTIFICIAL KEY TO THE GENERA OF FERNS AND FERN ALLIES
1. Plant a free-living gametophyte, consisting of filaments or thalli, generally a single cell thick, usually with abundant single-celled gemmae......Key A 1. Plant a sporophyte, consisting of a stem, rhizome, corm, or crown producing well-developed leaves, more than 1 cell thick (except in Trichomanes and Hymenophyllum), generally reproducing by spores......24. Leaf blades medium to large, more than 30 cm long or wide......6
Key A -- Pteridophytes reduced to thalloid or filamentous, free-living gametophytes
1. Gametophytes filamentous......Trichomanes (HYMENOPHYLLACEAE)1. Gametophytes thalloid, ribbon-like and branched......2
2. Gemmae uniseriate (1 cell wide)...... Vittaria appalachiana (VITTARIACEAE)
Key B -- Pteridophytes growing as floating or rooted aquatics
1. Plant a floating aquatic......21. Plant a rooted aquatic......3
2. Leaves 5-15 mm long, bright green, with obvious hairs on the upper surface...... Salvinia (SALVINIACEAE)
3. Leaves linear......4
4. Plants rhizomatous, the leaves reduced to a winged stipe......Pilularia americana (MARSILEACEAE)
Key C -- Pteridophytes with leaves not "fern-like" (unlobed, variously awl-shaped, scale-like, or terete)
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 ......Equisetum (EQUISETACEAE)1. Stem 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
2. Leaves various (scale-like, awl-like, moss-like, or flat), but not linear and grass-like, mostly 1-10H as long as wide......5
3. Leaves numerous from a corm or short rhizome; sporangia either borne in the expanded leaf bases (Isoetes) or in 2 rows at the tip of the linear fertile leaves (Schizaea).....4
4. Leaves notably spiral-curly, from a short rhizome; sporangia borne in 2 rows at the tip of the linear fertile leaves......Schizaea pusilla (SCHIZAEACEAE)
5. Leaves either larger or, if scale-like, with nerves and longer than the internodes (the leaves thus overlapping); sporangia yellowish to brownish, 1-locular, less than 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, Diphasiastrum, and Lycopodium )(LYCOPODIACEAE)......6
6. Plant with leaves not as above (see below)......12
7. 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 of one size......8
8. 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......9
9. Leaves rigid, bright to dark green, shiny, evergreen; leafy stems mainly erect, treelike, fanlike, or creeping (if creeping, then the leaves with elongate, hyaline hair-tips); rhizome trailing, perennial; [plants of uplands, mostly in moist to dry soils]......11
10. Leaves of the prostrate stems 1.3-2.1 mm wide, not toothed; leaves of the erect stem few, not overlapping, whorled; leaves of the strobilus much reduced relative to leaves of the prostrate and upright stems; upright stems 1.5-3 mm in diameter (including the leaves) ......Pseudolycopodiella caroliniana (LYCOPODIACEAE)
11. Shoots round-branched, usually 5-8 mm wide (including the leaves), leaves awl-shaped, monomorphic (though sometimes differing in size), separate, spreading or ascending, in 6 ranks; strobili sessile at stem apices......Lycopodium (LYCOPODIACEAE)
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
13. Leaf blades 0.3-1.6 cm long, cuneate at the base, rounded to 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, 0.1-0.3 mm in diameter, the leaves scattered along it......Trichomanes petersii (HYMENOPHYLLACEAE)
Key D -- Small pteridophytes, epipetric or epiphytic, growing on rock, tree bark, walls, or over rock in thin soil mats or in small soil pockets
1. Leaves pinnatifid or bipinnatifid, most of the pinnae not fully divided from one another (the rachis winged by leaf tissue most or all of its length)......21. Leaves pinnate, pinnate-pinnatifid, 2-pinnate, or even more divided (the rachis naked for most of its length, often winged in the apical portion)......7
2. Leaves pinnatifid, the pinnae not lobed......4
3. Lowermost pinnae with a few, irregular lobes (the upper pinnae unlobed) ......Pteris multifida (PTERIDACEAE)
4. Leaves without a long-attenuate apex, blade lobed for most of its length; sori round......5
5. Plants larger, the leave blades 7-30 cm long; [plants occurring on moist to dry habitats]......6
6. Leaf blade scaleless on the lower surface; leaf segment margins denticulate; rhizome 3-6 mm in diameter......Polypodium (POLYPODIACEAE)
7. Leaves bipinnate or more divided......13
8. Leaves of an herbaceous, subcoriaceous, or coriaceous texture, more than 1 cell thick; sori otherwise; [plants of various habitats, not strictly of moist sites]......10
9. Indusium ("involucre") tubular or funnelform, sometimes slightly 2-lobed; receptacle long and whiplike, exserted from the mouth of the tubular indusium......Trichomanes (HYMENOPHYLLACEAE)
10. Pinnae less than 1 cm wide; leaves herbaceous to subcoriaceous; veins free, not rejoining......11
11. Sori on the undersurface of the leaf, marginal and more-or-less hidden beneath either the unmodified revolute leaf margin or under a modified, reflexed false indusium......12
12. Rachis green or tan; leaf margin modified into a false indusium, reflexed to cover the sori ......Pteris vittata (PTERIDACEAE)
13. Leaf blade elongate, mostly lanceolate, generally 4H or more as long as wide (except in Adiantum capillus-veneris, with leaf blade often only 1.5 -3H as long as wide, but not notably triangular or pentagonal in outline)......15
14. Leaf blade broadly triangular in outline, the basal pinnae by far the largest; rhizome ca. 1 mm in diameter; indusia absent;[ native species of mountain peaks of n. NC and VA] ......Gymnocarpium appalachianum (DRYOPTERIDACEAE)
15. Sori not marginal, either naked , or slightly to strongly hidden by indusia......18
16. Sori continuous along the pinnule margins; leaves mostly dark-green or glaucous, often pubescent, coriaceous, tough, and stiff......17
17. Leaves 1-2-pinnate, the ultimate leaf-segments 8-100 mm long, glabrous or sparsely and inconspicuously hairy......Pellaea (PTERIDACEAE)
18. Leaf blades 4-30 (-50) cm long; sori globular, surrounded or covered by an entire, ciliate, or divided indusium......19
19. Veins ending short of the margin; indusium attached under the sorus, cuplike (divided into 3-6 lanceolate to ovate lobes which surround the sorus from below) or of minute numerous septate hairs, which extend out from under the sorus on all sides; petioles often densely beset with scales, the petiole bases persistent......Woodsia (DRYOPTERIDACEAE)
Key E -- Small pteridophytes, terrestrial, growing in soil, not associated with rock outcrops
1. Petiole branched once dichotomously, each branch bearing 3-7 pinnae in one direction only, the outline of the blade fan-shaped, often broader than long......Adiantum pedatum (PTERIDACEAE)1. Petiole not branched dichotomously, the outline of the blade either longer than broad or triangular and about as wide as long......2
2. Leaves pinnate, pinnate-pinnatifid, 2-pinnate, or even more divided (the rachis naked for most of its length, often winged in the apical portion)......6
3. Sporangia either borne on normal leaf blades or on specialized (fertile) leaves separate from the rhizome......4
4. Leaves dimorphic, the sori borne on leaves significantly different than normal leaves......5
5. Fertile leaf stiff but herbaceous, green, the pinnae linear, not at all bead-like; pinnae margins finely serrulate, otherwise slightly wavy or straight; pinnae mostly with acute apices, tending to be borne alternate......Woodwardia areolata (BLECHNACEAE)
6. Leaves lanceolate in outline, much longer than broad; sporangia either borne on normal leaf blades, on slightly dimorphic blades, or on an erect stalk that arises at or above ground level from the stipe of the sterile leaf blade (joining the stipe of the sterile leaf above the rhizome)......7
7. Leaf blades10-30 (-100) cm long; sporangia either borne on normal leaf blades or on slightly dimorphic blades......8
8. Leaves light to medium green, herbaceous, deciduous to semi-evergreen......9
9. Sori round; leaf blades monomorphic; the larger leaf blades 5-15 cm wide......Thelypteris (THELYPTERIDACEAE)
Key F -- Medium to large pteridophytes, epipetric, growing on rock, walls, or over rock in thin soil mats or in small soil pockets
1. Leaves vine-like, 0.3-10 m long, the branching dichotomous, 1 branch of each dichotomy terminating in a pair of pinnae, the pinnae often widely spaced (more than 10 cm apart) ......Lygodium (LYGODIACEAE)1. Leaves not vine-like, 0.3-1 m long, the branching not as described above, the pinnae regularly and more-or-less closely spaced (mostly less than 10 cm apart)......2
2. Leaves 2-pinnate or more divided, the pinnae divided to their midribs......9
3. Sori neither marginal nor continuous, slightly to entirely covered by an elongate or roundish indusium (sometimes ciliate, toothed, or divided into narrow segments); pinnae usually at least in part alternate, mostly lanceolate, toothed, lobed, or pinnatifid......4
4. Sori circular or globular, the indusium peltate, reniform, or cuplike; leaf blades (if more than 30 cm long) more than 5 cm wide......5
5. Leaves 1-pinnate-pinnatifid, the pinnae pinnatifid, generally lacking a prominent basal lobe, light green to dark green, herbaceous to subcoriaceous; indusium either reniform or cuplike......7
6. Veins branching dichotomously, free, not rejoining to form a netlike pattern; pinnae 25-50 pairs on larger leaves; [plant a common native species] ......Polystichum (DRYOPTERIDACEAE)
7. Vascular bundles in the petiole 2, uniting above......8
8. Indusium cuplike, attached beneath the sorus and consisting of 3-6 lanceolate to ovate segments......Woodsia obtusa (DRYOPTERIDACEAE)
10. Leaf blades elongate, mostly lanceolate, generally 4H or more as long as wide......12
11. Leaf blade broadly triangular in outline, the basal pinnae the largest; sori marginal, linear, indusium absent, protected by the revolute leaf margin and a minute false indusium......Pteridium (DENNSTAEDIACEAE)
12. Outline of the leaf blade slightly if at all narrowed to the base, the widest point less than 5 pinna pairs from the base, the lowermost pinnae more than 1/2 as long as the longest pinnae; rhizomes short-creeping, the leaves clustered, not forming clonal patches (or with rhizomes long-creeping, leaves scattered, forming clonal patches in Dennstaedtia)......13
13. Rhizomes short-creeping, the leaves clustered, not forming clonal patchesascular bundles in the petiole 2-7 (sometimes uniting to 1 in the upper petiole); sori mostly larger, mostly not marginal, the indusium not as above (though cuplike in Woodsia obtusa); leaf blades either glabrous, glabrescent, with flattened scales, or puberulent with glandular trichomes......14
14. Vascular bundles 2 in the petiole (or uniting near the leaf blade into 1)......15
15. Leaves 5-25 (-30) cm wide, with scales and minute glands (sometimes also with septate hairs); [native species, widespread]......16
16. Leaves 2-pinnate-pinnatifid; indusium flaplike or pocketlike, attached at one side of the sorus and arching over it......17
17. Leaves 4-9 cm wide, the tip long-attenuate; indusium pocketlike or hoodlike......Cystopteris bulbifera (DRYOPTERIDACEAE)
Key G -- Medium to large pteridophytes, terrestrial, growing in soil, not associated with rock outcrops
1. Leaves vine-like, 0.3-10 m long, the branching dichotomous, 1 branch of each dichotomy terminating in a pair of pinnae, the pinnae often widely spaced (more than 10 cm apart)......Lygodium (LYGODIACEAE)1. Leaves not vine-like, 0.3-3 m long, the branching not as described above, the pinnae regularly and more-or-less closely spaced (mostly less than 10 cm apart)......2
2. Leaves elongate in outline, mostly ovate, lanceolate, oblanceolate, or narrowly triangular, 1.5-10H or more as long as wide......6
3. Leaf blades pentagonal or broadly triangular in outline, the petiole not branched dichotomously......4
4. Leaf blade broadly triangular in outline, the basal pinnae the largest; sori marginal, linear, indusium absent, protected by the revolute leaf margin and a minute false indusium (Pteridium), or sporangia borne in a stalked, specialized, fertile portion of the blade (Botrychium)......5
5. Sporangia borne in a stalked, specialized, fertile portion of the blade; texture of mature leaf blades hard and stiff; plants colonial from deep-seated rhizomes; [plants primarily of moist to dry woodlands and savannas] ......Pteridium (DENNSTAEDIACEAE)
6. Leaves 1-pinnate-pinnatifid or less divided, the pinnae entire, toothed, lobed or pinnatifid......13
7. Leaf blade not divided into sterile and fertile portions (though often not all pinnules on a leaf bearing sporangia), the pinnules bearing sporangia only slightly if at all reduced in size, both fertile and sterile pinnules usually 4-20 mm long and 2-10 mm wide......8
8. Rhizomes short-creeping, the leaves clustered, not forming clonal patches; vascular bundles in the petiole 2-7 (sometimes uniting to 1 in the upper petiole); sori mostly larger, mostly not marginal, the indusium not as above (though cuplike in Woodsia obtusa); leaf blades either glabrous, glabrescent, with flattened scales, or puberulent with glandular trichomes......9
9. Vascular bundles 2 in the petiole (or uniting near the leaf blade into 1)......10
10. Leaves 5-25 (-30) cm wide, with scales and minute glands (sometimes also with septate hairs); [native species, widespread]......11
11. Leaves 2-pinnate-pinnatifid; indusium flaplike or pocketlike, attached at one side of the sorus and arching over it......12
12. Leaves 4-9 cm wide, the tip long-attenuate; indusium pocketlike or hoodlike......Cystopteris bulbifera (DRYOPTERIDACEAE)
13. Leaves 1-pinnate or 1-pinnate-pinnatifid, the pinnae fully divided from one another (the rachis naked for most of its length, often winged in the terminal portion); leaves dimorphic or not......15
14. Fertile leaf stiff but herbaceous, green, the pinnae linear, not at all bead-like; pinnae margins finely serrulate, otherwise slightly wavy or straight; pinnae mostly with acute apices, tending to be borne alternate......Woodwardia areolata (BLECHNACEAE)
16. Sori elongate, borne end to end along either side of the main veins; pinna lobes of sterile leaves with reticulate, chain-like venation along the central vein ......Woodwardia virginica (BLECHNACEAE)
17. Plants mostly less robust, the leaves 3-10 dm tall (except Dryopteris ludoviciana, D. celsa, and D. goldiana to 15 dm); leaves not at all or only slightly dimorphic, the fertile differing in various ways, such as having narrower pinnae (as in Dryopteris ludoviciana, Polystichum acrostichoides, Diplazium, and Thelypteris palustris) or the fertile leaves taller and more deciduous (as in Asplenium platyneuron and Dryopteris cristata), but not as described in the first lead; rachises and petioles variously scaly or scaleless, but at least the petiole and often also the rachis scaly if the plants over 1 m tall......19
18. Leaves slightly if at all tapering to the base, about equally broad through much of their length, the basalmost pinnae much more than 1/2 as long as the largest pinnae......Osmunda (OSMUNDACEAE)
19. Sori roundish, the indusium kidney-shaped or roundish, attached by a central stalk......22
20. Stipe and rachis green; fertile leaves 10-20 (-30) cm wide......20
21. Leaves 1-pinnate (the pinnae entire) ......Diplazium pycnocarpon (DRYOPTERIDACEAE)
22. Leaves 1-pinnate-pinnatifid, the pinnae pinnatifid, generally lacking a prominent basal lobe, light green to dark green, herbaceous to subcoriaceous; indusium reniform......23
23. Vascular bundles in the petiole 2, uniting above......Thelypteris (THELYPTERIDACEAE)
Flora of the Carolinas and Virginia, Working Draft of 27 October 1997 -- KEY TO PTERIDOPHYTE GENERA. Alan S. Weakley. The Nature Conservancy, Southeast Regional Office, Southern Conservation Science Department.