ASPLENIACEAE (Spleenwort Family)

This family consists of a single genus, Asplenium, with about 720 species.

Asplenium Linnaeus (Spleenwort)

References: Wagner, Moran, & Werth in FNA (1993b); Moran (1982); Taylor, Mohlenbrock, & Burton (1976).

Asplenium is a large, semicosmopolitan genus, with about 720 species, with centers of diversity in the Applachians, Central America mountains, Andes, and Himalayas.

Note: several of the more frequently encountered sterile hybrids are included in the key and treated fully below.

1. Leaves pinnatifid (at least in the lower half of the leaf), pinnate, pinnate-pinnatifid, bipinnate, or tripinnate, the apex obtuse, acute, acuminate, or attenuate; veins free......4

2. Leaf blades 0-3 mm wide, linear, forking or with a few toothlike projections......[A. septentrionale]
2. Leaf blades 10-40 mm wide, lanceolate, lance-attenuate, or oblong......3

4. Rachis dull green throughout its length, or at least towards the tip; leaves pinnatifid to tripinnate, the outline of the leaf blade narrowly to broadly triangular, widest at the base......5

4. Rachis shiny black or dark brown throughout its length; leaves pinnate, the outline of the leaf blade linear, lanceolate, or oblanceolate, with more-or-less parallel sides for much of its length......

5. Petiole partially or entirely green (darkened or not at its base)......7

6. Leaves bipinnate at the base, pinnate-pinnatifid above; spores normal...... A. bradleyi
6. Leaves pinnate at the base, pinnatifid above; spores abortive (very rarely normal, outside of our area)...... A. Hebenoides

7. Leaves bipinnate to tripinnate......9

8. Leaves pinnatifid, sometimes fully pinnate at the base; spores normal...... A. pinnatifidum
8. Leaves pinnate, sometimes pinnate-pinnatifid at the base; spores abortive...... A. Htrudellii

10. Pinnae orbicular to obovate-oblong, 1-2H as long as wide, the base more-or-less symmetrical (if auriculate, only slightly so and on the side of the pinna towards the base of the leaf); old leaf rachises often with persistent projections left from the disarticulation of the pinnae......11

10. Pinnae oblong-rectangular, 2H or more as long as wide, the base asymmetrical or auricled (more prominently auricled on the side of the pinna towards the tip of the leaf); old leaf rachises lacking persistent projections left from the disarticulation of the pinnae......12

12. Leaves slightly dimorphic, the fertile upright and larger, the sterile spreading and smaller; pinna auricles prominent, often overlapping the rachis; [plant terrestrial, often not associated with rock outcrops]......13

12. Leaves not dimorphic; pinna auricles less prominent, usually not overlapping the rachis; [plant epipetric, always growing in crevices of rock outcrops or in thin soil immediately adjacent to exposed rock]......14

14. Main vein of the pinna running along the basal edge; sori 1 (-3) per pinna, 1.5-3 mm long, borne along the basal edge, the indusium translucent, whitish, opening towards the leaf tip...... A. monanthes
14. Main vein of the pinna running more-or-less medially; sori 4-10 per pinna (on well-developed pinnae), 1.0-1.5 mm long, borne on both sides of the main vein, the indusium opaque, greenish, opening towards the pinna tip......15

Asplenium Hebenoides R.R. Scott (pro species) [A. platyneuron H rhizophyllum], Scott's Spleenwort. Mt (NC, VA), Pd, Cp (VA): moist outcrops of calcareous sedimentary rocks, such as limestone, dolostone, and on coquina limestone (shell marl), at low elevations; rare. May-October. Ranging from VT, NJ, PA, OH, s. IL, and MO south to e. VA, w. NC, c. AL, TN, and AR. So far as is known, A. Hebenoides is a sterile hybrid throughout our range (chromosome complement symbolized PR). In AL, however, one population has undergone chromosome doubling and is a fertile allotetraploid (PPRR). Populations of this taxon, especially if consisting of many individuals, should be checked for fertile spores. [HAsplenosorus ebenoides (R.R. Scott) Wherry -- F; Asplenosorus ebenoides (R.R. Scott) Wherry -- G; Asplenium ebenoides R.R. Scott -- FNA, K, S]

Asplenium heteroresiliens W.H. Wagner, Carolina Spleenwort. Cp (NC, SC): fairly moist outcrops of calcareous sedimentary rocks, such as coquina limestone ("marl"), along small blackwater streams or larger rivers, at low elevations; rare (US Species of Concern, NC Endangered, SC Rare List). April-October. Rare and scattered from se. NC to se. GA, sw. GA, and n. FL, on the Coastal Plain. This species is an apogamous (producing viable spores asexually) allopentaploid derived from hybridization of the sexual tetraploid H. heterochroum Kunze (of Florida and the West Indies) and the apogamous triploid A. resiliens. Its chromosome complement can be symbolized EEEHH. [= RAB; A. Hheteroresiliens -- FNA, K; A. heterochroum Kunze -- S, in part]

Asplenium monanthes Linnaeus, Single-sorus Spleenwort. Mt (NC, SC): moist outcrops of calcareous to semi-calcareous metamorphic rocks, such as mylonite or marble, near waterfalls in humid escarpment gorges with high rainfall, at low elevations; rare (NC Endangered, SC Rare List). April-October. This species is scattered in highly humid (montane or maritime) parts of the New World and Old World tropics, known from the West Indies (Hispaniola and Jamaica), n. South America, Central America, Mexico, South Africa, Hawaii, and Sandwich Islands, the Azores, Madeira Islands, Madagascar, and the Philippines. In the continental United States, it is known from humid escarpment gorges in Transylvania County, NC and Oconee County, SC, from limestone talus in the collapsed mouth of a sinkhole in Jackson County, AL, and from the Huachuca Mountains, Cochise County, AZ. [= RAB, FNA, K, W]

Asplenium montanum Willdenow, Mountain Spleenwort. Mt, Pd (NC, SC, VA): moist to dry outcrops of metamorphic, sedimentary, or igneous rocks, such as gneiss, schist, amphibolite, quartzite, rhyolite, sandstone, mostly at moderate to high elevations (up to over 2000m), but in the Piedmont to as low as 150 m; common. May-October. Primarily Appalachian, ranging from s. VT, MA, NY, OH, and KY south to c. NC, n. GA and AL; absent from the Ozarkian highlands. A. montanum is one of the diploid progenitors of the reticulately evolved Appalachian Asplenium complex; its chromosome complement is symbolized MM. It is one parent of A. bradleyi, A. pinnatifidum, and A. Htrudellii (and of other sterile hybrids). [= RAB, C, F, FNA, G, K, S, W]

Asplenium platyneuron (Linnaeus) Britton, Sterns, & Poggenberg var. bacculum-rubrum (Featherman) Fernald, Maritime Ebony Spleenwort. Cp (NC, SC, VA): sandy soils (often with substantial shell hash) of maritime forests, aboriginal shell middens, at low elevations; rare (NC Watch List, VA Watch List). April-October. Ranging from se. VA south to FL and west to LA, probably restricted to the Coastal Plain. [= F, G, K; A. platyneuron -- RAB, C, FNA, S, W, in part only (infraspecific taxa not distinguished)]

Asplenium platyneuron (Linnaeus) Britton, Sterns, & Poggenberg var. platyneuron, Common Ebony Spleenwort. Mt, Pd, Cp (NC, SC, VA): moist to dry soils of forests, woodlands, old fields; also on outcrops, especially of calcareous rocks, at low to moderate elevations; common. April-October. Ranging from QuJbec, Ontario, se. MN, IA, and se. CO south to FL, TX, NM, and AZ (and varieties or relatives reported from Central and South America). This species is one of the diploid progenitors involved in the reticulately evolved Appalachian Asplenium complex. It is one parent of A. bradleyi and A. Hebenoides (as well as other sterile hybrids). A. platyneuron in general, and var. platyneuron specifically, is by far the most common of our Asplenia, and the only one found characteristically away from rock. A. platyneuron var. incisum does not seem to warrant taxonomic recognition. [= F, G, K; A. platyneuron -- RAB, C, FNA, S, W, in part only (infraspecific taxa not distinguished; including A. platyneuron var. incisum (Howe ex Peck) B.L. Robinson -- F, K]

Asplenium resiliens Kunze, Blackstem Spleenwort. Mt (NC, SC, VA), Pd (VA): moist to dry outcrops of calcareous sedimentary or metamorphic rocks, such as limestone, dolostone, or marble, sometimes on narrow seams of calcareous materials in otherwise acidic rocks, mostly at low to moderate elevations, but remarkably on Grandfather Mountain at over 1800m; common in VA, rare in VA Piedmont, NC, and SC (NC Watch List, SC Rare List). April-October. Ranging from s. PA, KY, s. IL, MO, se. KS, OK, TX, CO, and s, NV south to FL, TX, AZ, and Mexico; also in the West Indies, Central America, and South America. This species is a triploid (EEE), unable to produce viable spores by sexual means, but producing spores apogamously. It is a parent of the rare A. heteroresiliens. [= RAB, C, F, FNA, G, K, S, W]

Asplenium rhizophyllum Linnaeus, Walking Fern. Mt (NC, SC, VA), Pd, Cp (NC, VA): moist outcrops of calcareous sedimentary, calcareous metamorphic, or mafic metamorphic rocks, such as limestone, dolostone, calcareous siltstone, amphibolite, mostly at low to moderate elevations, rarely to 1500 m or higher; common (but local) in VA Mountains, uncommon in VA Piedmont, rare in VA Coastal Plain, uncommon in NC Mountains, rare in NC Piedmont and Coastal Plain (SC Rare List). May-October. Ranging from s. QuJbec, Ontario and se. MN south to n. GA, AL, MS, AR, OK, and IA. This species, sometimes placed in the genus Camptosorus because of its strikingly different morphology from (most) other Asplenium, is one of the diploid progenitors of the reticulately evolved Appalachian Asplenium complex. It is a parent of A. pinnatifidum and A. Hebenoides (as well as other sterile hybrids), both of which have inherited a limited ability to produce plantlets at the attenuate leaf-tip. It is closely related to Asplenium sibiricum of e. Asia. [= RAB, C, FNA, K, W; Camptosorus rhizophyllus (Linnaeus) Link -- F, G, S]

Asplenium ruta-muraria Linnaeus var. cryptolepis (Fernald) Wherry, American Wall-rue. Mt (NC, VA), Pd (VA): moist to dry outcrops of calcareous sedimentary or metamorphic rocks, such as limestone, dolostone, or marble, at low to moderate elevations; uncommon in VA (rare in Piedmont, rare in NC). May-October. A. ruta-muraria is a circumboreal species of Europe, Asia, and North America; in North America it ranges as var. cryptolepis from VT, s. Ontario and n. MI south to n. NJ, w. NC, n. AL, TN, and AR. Var. ohionis is very likely only a form. The relationship of North American A. ruta-muraria (here distinguished as var. cryptolepis), a tetraploid, to the diploid and tetraploid subspecies of A. ruta-muraria present in Europe and e. Asia is uncertain. Given the prevalence of allopolyploidy in Asplenium and slight morphologic differences between American and European material, I prefer not to assume its identity to the European plants. In Europe A. ruta-muraria is an abundant plant of masonry, such as the defensive walls of towns and cities; it is very rarely seen on walls in North America, presumably because they are not old enough. [= G, K; A. ruta-muraria -- RAB, C, FNA, W, infraspecific taxa not distinguished; A. cryptolepis Fernald var. cryptolepis -- F, S; including A. cryptolepis Fernald var. ohionis Fernald -- F, S; including A. ruta-muraria var. ohionis (Fernald Wherry -- G, S; including A. ruta-muraria var. lanceolum Christ -- K]

Asplenium trichomanes Linnaeus ssp. quadrivalens D.E. Meyer emend. Lovis, Maidenhair Spleenwort. Mt (VA): moist outcrops of calcareous sedimentary rocks, such as limestone or dolostone; rare (VA Watch List). May-October. Ssp. quadrivalens is known from North America and Europe (at least); in North America it is substantially rarer than ssp. trichomanes and more limited in range, occurring from New England and s. Ontario south to w. VA, OH, and s. IL, and in British Columbia, WA, and OR. Ssp. quadrivalens is a tetraploid of uncertain origin, presumably autotetraploid, but perhaps the result of the hybridization of 2 ecologically differentiated diploid races of A. trichomanes. [= FNA, K, W; A. trichomanes -- RAB, C, F, G, S, in part only, varieties not recognized]

Asplenium trichomanes Linnaeus ssp. trichomanes, Maidenhair Spleenwort. Mt, Pd (NC, SC, VA): moist outcrops of slightly to strongly calcareous sedimentary or metamorphic rocks and moderately to strongly mafic metamorphic and igneous rocks, such as limestone, dolostone, mafic and intermediate gneisses and schists, amphibolite, most typically in strong shade, as under overhangs; common (SC Rare List). May-October. A. trichomanes as a whole is a complex species, with diploid, tetraploid, and hexaploid elements, occurring in North America, Europe, Australia, New Zealand, and Asia. Ssp. trichomanes is known to occur in Europe and North America (at least); in North America, it ranges from Newfoundland to AK, south to NC, c. AL, AR, OK, w. TX, se. AZ, and w. OR. Ssp. trichomanes is a diploid, probably involved in the origin of ssp. quadrivalens. [= FNA, K, W; A. trichomanes -- RAB, C, F, G, S, in part only, varieties not recognized]

Asplenium Htrudellii Wherry (pro species) [montanum H pinnatifidum], Trudell's Spleenwort. Pd (VA), Mt (NC, VA): moist outcrops of felsic sedimentary or metamorphic rocks, such as sandstone, phyllite, schist, at low elevations; rare. May-October. This taxon is a sterile triploid hybrid (MMR) of A. montanum and A. pinnatifidum. It is considerably more common than most other sterile Asplenium hybrids, sometimes occurring without one or either parents. There are some reports that it can sometimes produce fertile spores. [= F, K; Asplenium pinnatifidum Nuttall var. trudellii (Wherry) Clute -- G; Asplenium trudellii Wherry -- S; HAsplenosorus trudellii (Wherry) Mickel]

Asplenium septentrionale (Linnaeus) Hoffmann occurs in WV (Hardy and Monroe counties), close to the VA line. It occurs on acidic rocks and may well be found in our area, as it is so inconspicuous. [= C, FNA, K]

Asplenium scolopendrium Linnaeus var. americanum (Fernald) Kartesz & Gandhi, American Hart's-tongue Fern, is a very rare taxon, occurring in humid sinkholes in e. TN and n. AL, and other habitats, farther north in c. NY, n. MI, and Ontario; it is also reported as naturalized in MD by Reed (1953). [= FNA, K; Phyllitis scolopendrium (Linnaeus) Newman var. americana Fernald -- C]

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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.