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FERNS AND FERN ALLIES

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......2

3. Leaves not "fern-like," unlobed, variously awl-shaped, scale-like, or terete......Key C

3. Leaves "fern-like," variously lobed or divided, ranging from pinnatifid to 4-pinnate......4

5. Plants epipetric or epiphytic, growing on rock, tree bark, walls, or over rock in thin soil mats or in small soil pockets......Key D

5. Plants terrestrial, growing in soil, not associated with rock outcrops......Key E


Key A -- Pteridophytes reduced to thalloid or filamentous, free-living gametophytes

1. Gametophytes filamentous......Trichomanes
(HYMENOPHYLLACEAE)

1. Gametophytes thalloid, ribbon-like and branched......2


Key B -- Pteridophytes growing as floating or rooted aquatics

1. Plant a floating aquatic......2

1. Plant a rooted aquatic......3

3. Plant cloverlike, with 4 leaf segments borne terminally......Marsilea quadrifolia (MARSILEACEAE)

3. Leaves linear......4


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

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......Pilularia americana (MARSILEACEAE)

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

5. Leaves inconspicuous, reduced to a few nerveless scales (less than 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......Psilotum nudum (PSILOTACEAE)

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

7. Sporangia borne in flattened or quadrangular strobili sessile at the tips of leafy branches; spores and sporangia of two sizes, the megasporangia larger and borne basally in the strobili......Selaginella (SELAGINELLACEAE)

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

9. Leaves herbaceous, pale or yellow-green, dull, deciduous; leafy stems creeping; rhizome dying back annually to an underground vegetative tuber at apex; [plants of wetlands, mostly on moist or wet sands or peats]......10

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

11. Shoots flat-branched, 1-3 mm wide (including the leaves); leaves scalelike, dimorphic, overlapping and imbricate, appressed to the stem, in 4 ranks; strobili on long, narrow peduncles......Diphasiastrum (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)

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 in 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......Asplenium rhizophyllum (ASPLENIACEAE)

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)......2

1. 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

3. Lowermost (and other) pinnae with numerous, rather even lobes......Phegopteris (THELYPTERIDACEAE)

3. Lowermost pinnae with a few, irregular lobes (the upper pinnae unlobed) ......Pteris multifida (PTERIDACEAE)

5. Plants dwarf, the leave blades less than 5 cm long; [plants occurring only in permanently moist habitats, as in grottoes behind waterfalls] ......Grammitis nimbata (GRAMMITIDACEAE)

5. Plants larger, the leave blades 7-30 cm long; [plants occurring on moist to dry habitats]......6

7. Leaves pinnate or pinnate-pinnatifid......8

7. Leaves bipinnate or more divided......13

9. Indusium ("involucre") bivalvate (deeply divided into 2 flaps); receptacle not exserted from between the 2 flaps of the indusium......Hymenophyllum (HYMENOPHYLLACEAE)

9. Indusium ("involucre") tubular or funnelform, sometimes slightly 2-lobed; receptacle long and whiplike, exserted from the mouth of the tubular indusium......Trichomanes (HYMENOPHYLLACEAE)

11. Sori on the undersurface of the leaf, away from the margins......Asplenium (ASPLENIACEAE)

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

13. Leaf blade pentagonal or broadly triangular in outline, ca. 1H as long as wide......14

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

15. Sori marginal, usually more-or-less hidden under the revolute margin of the pinnule......16

15. Sori not marginal, either naked , or slightly to strongly hidden by indusia......18

17. Leaves 2-3-pinnate, the ultimate leaf-segments 1-4 (-8) mm long, more-or-less densely hairy (glabrous in C. alabamensis) ......Cheilanthes (PTERIDACEAE)

17. Leaves 1-2-pinnate, the ultimate leaf-segments 8-100 mm long, glabrous or sparsely and inconspicuously hairy......Pellaea (PTERIDACEAE)

19. Veins reaching the margin; indusium attached under one side of the sorus, hoodlike or pocketlike, arching over the sorus; petioles glabrous or sparsely beset with scales, the petiole bases not persistent......Cystopteris (DRYOPTERIDACEAE)

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

3. Sporangia borne 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......Botrychium (OPHIOGLOSSACEAE)

3. Sporangia either borne on normal leaf blades or on specialized (fertile) leaves separate from the rhizome......4

5. Fertile leaf woody, brown, with bead-like segments; pinnae margins entire, often wavy or the lowermost even somewhat lobed; pinnae mostly with obtuse apices, tending to be borne opposite......Onoclea sensibilis var. sensibilis (DRYOPTERIDACEAE)

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)

7. Leaf blades 1-8 cm long; sporangia borne 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) ......Botrychium (OPHIOGLOSSACEAE)

7. Leaf blades10-30 (-100) cm long; sporangia either borne on normal leaf blades or on slightly dimorphic blades......8

9. Sori elongate; leaf blades somewhat dimorphic, the fertile larger and erect, the sterile smaller and prostrate, the larger leaf blades 2-4 (-6.5) cm wide......Asplenium platyneuron (ASPLENIACEAE)

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

3. Sori marginal, continuous, covered by a reflexed false indusium along the leaf margin; pinnae usually opposite, linear, not toothed or lobed......Pteris vittata (PTERIDACEAE)

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

5. Leaves 1-pinnate, the pinnae toothed and each with a slight to prominent lobe near the base on the side towards the leaf tip, dark green, subcoriaceous to coriaceous; indusia peltate......6

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

7. Vascular bundles in the petiole 3-7......Dryopteris (DRYOPTERIDACEAE)

7. Vascular bundles in the petiole 2, uniting above......8

9. Sori marginal and borne on the underside of the false indusium; petioles and rachis shiny black or reddish-black, glabrous except at the very base of the petiole; pinnules fan-shaped or obliquely elongate......Adiantum (PTERIDACEAE)

9. Sori not marginal, borne on the undersurface of the leaf blade (if marginal, as in Pteridium and Dennstaedtia, borne on the undersurface of the leaf); petioles darkened only basally (if at all), rachis green, tan, or reddish; pinnules not notably fan-shaped or obliquely elongate......10

11. Leaf blade pentagonal in outline, the terminal pinna the largest; sori submarginal, roundish, the indusium reniform......Arachniodes simplicior (DRYOPTERIDACEAE)

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)

13. Rhizomes long-creeping, leaves scattered, forming clonal patches; vascular bundles in the petiole 1, U-shaped (even in the lower petiole); sori very small, marginal in sinuses, the indusium cuplike, 2-parted, the outer part a modified tooth of the leaf blade; leaf blades conspicuously puberulent with septate hairs......Dennstaedtia (DENNSTAEDIACEAE)

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

15. Leaves 25-65 cm wide, with whitish, straight, acicular hairs; [species adventive and weedy, presently known in our area only from the Coastal Plain of SC] ......Macrothelypteris (THELYPTERIDACEAE)

15. Leaves 5-25 (-30) cm wide, with scales and minute glands (sometimes also with septate hairs); [native species, widespread]......16

17. Leaves 10-30 cm wide, the tip acute to acuminate; indusium flaplike......Athyrium (DRYOPTERIDACEAE)

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

3. Leaf blades flabellate or fan-shaped in outline, the petiole branched once dichotomously, each branch bearing 3-7 pinnae in one direction only......Adiantum pedatum (PTERIDACEAE)

3. Leaf blades pentagonal or broadly triangular in outline, the petiole not branched dichotomously......4

5. Sporangia borne in marginal, linear sori, indusium absent, protected by the revolute leaf margin and a minute false indusium; texture of mature blades somewhat fleshy; plants solitary from a short underground rhizome with thick, mycorrhizal roots; [plants primarily of moist forests] ......Botrychium virginianum (OPHIOGLOSSACEAE)

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)

7. Leaf blade divided into sterile and fertile portions, the fertile pinnae basal, the sterile pinnules 30-70 mm long and 8-23 mm wide, serrulate, rounded basally, rounded to somewhat acute apically, the fertile pinnae terminal and greatly reduced in size, the fertile pinnules 7-11 mm long and 2-3 mm wide......Osmunda regalis var. spectabilis (OSMUNDACEAE)

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

9. Vascular bundles (3-) 5 (-7) in the petiole......Dryopteris (DRYOPTERIDACEAE)

9. Vascular bundles 2 in the petiole (or uniting near the leaf blade into 1)......10

11. Leaves 1-pinnate-pinnatifid; indusium cuplike, attached beneath the sorus and consisting of 3-6 lanceolate to ovate segments......Woodsia obtusa (DRYOPTERIDACEAE)

11. Leaves 2-pinnate-pinnatifid; indusium flaplike or pocketlike, attached at one side of the sorus and arching over it......12

13. Leaves 1-pinnatifid, most of the pinnae not fully divided from one another (the rachis winged by leaf tissue most or all of its length); leaves dimorphic, the fertile much modified, stiff and/or woody......14

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

15. Rhizomes long-creeping, leaves scattered, forming clonal patches......16

15. Rhizomes short-creeping, the leaves clustered, not forming clonal patches (or rhizomes of both types, but leaves borne only in clusters on the short erect ones, in Matteucia)......17

17. Plants moderately to very robust, the leaves typically 6-30 dm tall; leaves either strongly dimorphic, the fertile leaves very unlike the sterile, brown at maturity (Matteucia and Osmunda cinnamomea) or the fertile pinnae very unlike the sterile, brown at maturity, borne as an interruption in the blade, with normal green pinnae above and below (Osmunda claytoniana); rachises scaleless, petioles scaleless (except at the base in Matteucia)......18

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

19. Sori elongate, the indusium elongate, attached along one side as a flap......20

19. Sori roundish, the indusium kidney-shaped or roundish, attached by a central stalk......22

21. Leaves 1-pinnate-pinnatifid (the pinnae pinnatifid) ......Deparia acrostichoides (DRYOPTERIDACEAE)

21. Leaves 1-pinnate (the pinnae entire) ......Diplazium pycnocarpon (DRYOPTERIDACEAE)

23. Vascular bundles in the petiole 4-7......Dryopteris (DRYOPTERIDACEAE)

23. Vascular bundles in the petiole 2, uniting above......Thelypteris (THELYPTERIDACEAE)


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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.