Editing Asplenium platyneuron

{{Short description|Species of fern}}
{{Good article}}
{{Speciesbox
| name = Ebony spleenwort
| image = Asplenium platyneuron-fronds.jpg
| image_caption = ''A.&nbsp;platyneuron'' fronds; the smaller frond on the left is sterile, the longer frond on the right is fertile.
| image_alt = a picture of two simple, pinnately divided fern fronds, a shorter compact one on the left and a larger more open one on the right
| status = {{TNCStatus}}
| status_system = TNC
| status_ref = {{sfn|NatureServe|2024}}
| genus = Asplenium
| species = platyneuron
| authority = ([[Carl Linnaeus|L.]]) [[Nathaniel Lord Britton|Britton]], [[Emerson Ellick Sterns|Sterns]] & [[Justus Ferdinand Poggenburg I|Poggenb.]]
| synonyms = ''Acrostichum platyneuros'' <small>[[Carl Linnaeus|L.]]</small><br />
''Asplenium ebeneum'' <small>[[William Aiton|Aiton]]</small><br />
''Asplenium polypodioides'' <small>[[Olof Swartz|Sw.]]</small><br />
''Asplenium trichomanoides'' <small>[[André Michaux|Michx.]]</small> nom. illeg.<br />
''Chamaefilix platyneuros'' <small>([[Carl Linnaeus|L.]]) [[Farw.]]</small><br />
''Tarachia platyneura'' <small>([[Carl Linnaeus|L.]]) [[Momose]]</small>
}}

'''''Asplenium platyneuron''''' (syn. ''Asplenium ebeneum''), commonly known as '''ebony spleenwort''' or '''brownstem spleenwort''', is a fern native to North America east of the [[Rocky Mountains]]. It takes its common name from its dark, reddish-brown, glossy [[stipe (botany)|stipe]] and [[rachis]] (leaf stalk and midrib), which support a once-divided, [[pinnate]] leaf. The fertile [[frond]]s, which die off in the winter, are darker green and stand upright, while the sterile fronds are [[evergreen]] and lie flat on the ground. An [[auricle (botany)|auricle]] at the base of each pinna points towards the tip of the frond. The dimorphic fronds and alternate, rather than opposite, pinnae distinguish it from the similar [[Asplenium resiliens|black-stemmed spleenwort]].

The species was first described in 1753 by [[Carl Linnaeus|Linnaeus]] as ''Acrostichum platyneuros'', although Linnaeus' type drew on material from several other species as well. It was more commonly called ''Asplenium ebeneum'', a name published by [[William Aiton]] in 1789, until the rediscovery and revival of the Linnaean epithet in the late nineteenth century. Several forms and varieties of the species have been described, but few are recognized today; in particular, larger and more fertile specimens, those with more or less toothed leaves, and those with proliferating buds are considered to fall within the natural range of variation of the species, and do not require taxonomic distinction. ''A.&nbsp;platyneuron'' f.&nbsp;''hortonae'', a sterile form with the pinnae cut to toothed pinnules, and f.&nbsp;''furcatum'', with forking fronds, are still recognized.

The formation of proliferating buds is one of several unusual adaptations for reproduction in this species. The buds form near the base of the stipe, and when covered with soil, can grow into new individuals as the frond that bore them dies. Ebony spleenwort is also well-adapted to propagate by [[spore]]s: the upright sterile fronds help the spores enter the airstream for long-distance dispersal, and a low [[genetic load]] allows spores that have grown into a [[gametophyte]] to self-fertilize with a high degree of success. This dispersal ability seems to have helped the species spread rapidly in the [[Great Lakes]] region in the late 20th century. Long-distance dispersal may also explain its naturalized appearance in South Africa, and the existence of an isolated population found in [[Slovakia]] in 2009, its first known occurrence in Europe.

Ebony spleenwort has broad habitat preferences, growing both on rocks like many other North American [[spleenwort]]s and in a variety of soils. Unlike many other spleenworts, it is not particularly sensitive to [[soil pH]]. It hybridizes with several other spleenworts, particularly [[Asplenium montanum|mountain spleenwort]] and [[Asplenium rhizophyllum|walking fern]]; these species, their sterile hybrid offspring, fertile [[alloploid|allotetraploid]] hybrids, and [[backcross]]es between allotetraploids and the parents are collectively known as the "Appalachian ''Asplenium'' complex". Two hybrids between ''A.&nbsp;platyneuron'' and spleenworts outside of this complex are also known.

==Description==
Ebony spleenwort is a small fern with [[pinnate]] [[frond]]s, growing in tufts, with a shiny reddish-brown [[stipe (botany)|stipe]] and [[rachis]]. The fronds are [[frond dimorphism|dimorphic]], with long, erect, dark green fertile fronds, which are [[deciduous]], and shorter, spreading, lighter green sterile fronds, which are [[evergreen]].{{sfn|Cobb|Farnsworth|Lowe|2005|p=70}}

[[File:Asplenium platyneuron clump.JPG|left|300px|thumb|alt=small green fern, some fronds flat and some upright and arched|''Asplenium platyneuron'', showing fertile fronds (long and erect) and sterile fronds (short and spreading)]]

===Roots and rhizomes===
This fern does not spread and form new plants via the roots. The [[rhizome]], from {{convert|1|to|2.5|mm|in|sp=us|sigfig=1}}{{sfn|Lellinger|1985|p=240}} or perhaps {{convert|4|mm|in|sp=us|sigfig=1}} in diameter,{{sfn|Crouch|Klopper|Burrows|Burrows|2011|p=612}} bears a few{{sfn|Cobb|Farnsworth|Lowe|2005|p=70}} narrowly [[Glossary of leaf morphology#linear|linear]]-[[Glossary of leaf morphology#deltate|deltate]] scales, black to dark brown in color{{sfn|Wagner|Moran|Werth|1993}} and strongly clathrate (bearing a lattice-like pattern). The scales are {{convert|2|to|4|mm|in|sp=us|sigfig=1}}{{sfn|Wagner|Moran|Werth|1993}} or {{convert|5|mm|in|sp=us|sigfig=1}} long{{sfn|Crouch|Klopper|Burrows|Burrows|2011|p=612}} and {{convert|0.3|to|0.6|mm|in|sp=us|sigfig=1}} wide, with margins [[Glossary of leaf morphology#entire|entire]] (untoothed){{sfn|Wagner|Moran|Werth|1993}} or very nearly so.{{sfn|Crouch|Klopper|Burrows|Burrows|2011|p=612}}

===Leaves===
The stipe (the stalk of the leaf, below the blade) is {{convert|1|to|10|cm|in|sp=us|sigfig=1}} long, and comprises one-quarter to one-third of the length of the blade.{{sfn|Wagner|Moran|Werth|1993}} It lacks [[Glossary of botanical terms#wing|wing]]s,{{sfn|Lellinger|1985|p=240}} and is a shiny reddish-brown{{sfn|Wagner|Moran|Werth|1993}} or blackish-brown{{sfn|Crouch|Klopper|Burrows|Burrows|2011|p=612}} throughout its length. Towards the base, it has a few threadlike scales similar in color to those of the rhizome.{{sfn|Wagner|Moran|Werth|1993}} [[Starch]] granules are stored in tissue at the base of the stipe and, to a lesser extent, in the rhizome, giving the bases an enlarged appearance and a firm texture. The stipe bases are long-lived and may survive the disintegration of the rest of the stipe and the blade.{{sfn|Wagner|Johnson|1981|pp=159–160}}

The leaf blade of ebony spleenwort is linear to narrowly [[Glossary of leaf morphology#oblanceolate|oblanceolate]] (slightly wider in the upper half of the blade) in shape, measuring from {{convert|4|to|50|cm|in|sp=us|sigfig=1}} long and from {{convert|2|to|5|cm|in|sp=us|sigfig=1}} wide, sometimes as wide as {{convert|7|cm|in|sp=us|sigfig=1}}. It is [[Glossary of leaf morphology#acute|acute]] (pointed) at its tip and gradually tapers at its base. The blade is shiny and has a few scattered hairs, or lacks them entirely. The rachis (leaf axis), like the stipe, is reddish-, purplish- or blackish-brown, shiny and hairless.{{sfn|Wagner|Moran|Werth|1993}}{{sfn|Crouch|Klopper|Burrows|Burrows|2011|p=612}}

The blade is cut into [[leaflet (botany)|pinnae]] (leaflets) throughout its length, from 15 to 45&nbsp;pairs per leaf.{{sfn|Wagner|Moran|Werth|1993}} The pinnae are distinctly [[phyllotaxis|alternate]] along the rachis.{{sfn|Cobb|Farnsworth|Lowe|2005|p=70}} They are [[Glossary of leaf morphology#oblong|oblong]] (roughly rectangular) or quadrangular in shape,{{sfn|Wagner|Moran|Werth|1993}} sometimes somewhat [[Glossary of leaf morphology#falcate|falcate]] and angled towards the leaf base,{{sfn|Crouch|Klopper|Burrows|Burrows|2011|p=612}} those in the middle of the leaf blade measuring from {{convert|1|to|2.5|cm|in|sp=us|sigfig=1}} in length and from {{convert|0.3|to|0.5|cm|in|sp=us|sigfig=1}} in width. Each pinna has an obvious [[auricle (botany)|auricle]] at its base, pointing towards the tip of the blade and overlapping the rachis. Sometimes a small auricle pointing at the base of the blade is present as well The edges of the pinnae are [[Glossary of leaf morphology#crenate|crenate]] or [[Glossary of leaf morphology#serrulate|serrulate]] (bearing rounded or small sharp teeth); they are more deeply cut in small forms. The tips of the pinnae may be acute or [[Glossary of leaf morphology#obtuse|obtuse]] (blunt. On the underside of the blade, [[Leaf#Veins|veins]] are clearly visible and free (they do not [[anastomose]] or rejoin each other).{{sfn|Wagner|Moran|Werth|1993}} A few minute scales may also be scattered on the underside.{{sfn|Crouch|Klopper|Burrows|Burrows|2011|p=612}}

===Sori and spores===
Pinnae of the fertile fronds carry from one to twelve,{{sfn|Wagner|Moran|Werth|1993}} or even eighteen,{{sfn|Crouch|Klopper|Burrows|Burrows|2011|p=612}} pairs of [[sorus|sori]] on their underside, each {{convert|1|to|2|mm|in|sp=us|sigfig=1}} long.{{sfn|Lellinger|1985|p=240}} Each pair of sori forms a chevron, pointing towards the base of the pinna along its midvein, on which they are centered.{{sfn|Cobb|Farnsworth|Lowe|2005|p=71}}{{sfn|Lellinger|1985|loc=Pl. 366}} An [[indusium]] covers each sorus; these are whitish and translucent{{sfn|Lellinger|1985|p=240}} or silvery{{sfn|Cobb|Farnsworth|Lowe|2005|p=70}} with a slightly toothed or [[Glossary of botanical terms#erose|erose]] (irregularly jagged) edge,{{sfn|Lellinger|1985|p=240}} soon withering to reveal the sori.{{sfn|Cobb|Farnsworth|Lowe|2005|p=70}} Each [[sporangium]] in a sorus carries 64&nbsp;[[spore]]s. The diploid [[sporophyte]] has a chromosome number of 72.{{sfn|Wagner|Moran|Werth|1993}}

The light to dark brown{{sfn|Kinder|1966|p=30}} spores are [[monolete]], with a straight laesura{{efn|The laesura marks the line of division where a monolete spore splits from its sisters.}} with a margo (raised border). They are 41 to 52 microns long along their long axis. The perine (outermost layer of the spore) appears spiny, with rough ridges forming a netted pattern.{{sfn|Belling|Heusser|1975|pp=116, 120}} The region of the perine between ridges has a smooth, rather than granular, texture.{{sfn|Oliver|1968|p=11}}

===Proliferating buds===
Ebony spleenwort is capable of proliferating by forming new plantlets from buds on the rachis at the base of the plant. These allow new individuals to form at different levels when prostrate fronds become buried in the leaf litter.{{sfn|Wagner|Moran|Werth|1993}} Wagner & Johnson found proliferous buds in almost every site in the [[Great Lakes]] populations they studied; very rarely did more than one bud per plant occur. They occurred, on average, on 1 out of 6 plants, both on sterile and fertile fronds, and their position at the base of the lowest pinnae made them difficult to find among the cluster of fronds. The buds are button-like, pale in color, and appear on the upper side of the lowest pinnae. Each bud contains a [[meristem|shoot]] and one or sometimes two leaf [[primordium|primordia]], covered in clathrate scales, occasionally with roots if the bud has begun to develop. Contact with soil at the plant base stimulates their development, and the decay of their connection with the parental leaf results in the development of a new plant. Similar buds have also been reported from the single-sorus spleenwort, ''[[Asplenium monanthes]]''.{{sfn|Wagner|Johnson|1981|pp=160–161}}

===Identification===
The species most similar to ''Asplenium platyneuron'' is the black-stemmed spleenwort, ''[[Asplenium resiliens|A.&nbsp;resiliens]]''. However, this stipe of this species is darker, and the pinnae are opposite, rather than alternate, along the rachis.{{sfn|Cobb|Farnsworth|Lowe|2005|p=72}} Maidenhair spleenwort, ''[[Asplenium trichomanes|A.&nbsp;trichomanes]]'', is also pinnately cut with a dark, glossy rachis, but the pinnae are oval and somewhat rounded rather than broadly oblong, usually less than two times as long as wide.{{sfn|Diggs|Lipscomb|2014|p=102}}{{sfn|Crouch|Klopper|Burrows|Burrows|2011|p=612}} Neither of these two species, nor the other pinnate American spleenworts, have dimorphic fertile and sterile fronds.{{sfn|Lellinger|1985|p=231}} It is very similar to Boydston's spleenwort, ''[[Asplenium × boydstoniae]]'', an extremely rare [[backcross]] with Tutwiler's spleenwort, ''[[Asplenium tutwilerae]]''; however, Boydston's spleenwort has an elongated, acute frond tip similar to that of Tutwiler's spleenwort.{{sfn|Wagner|1956|pp=80–81}} Among similar South African spleenworts, ''[[Asplenium lunulatum|A.&nbsp;lunulatum]]'' has proliferating frond tips, while ''A.&nbsp;monanthes'' has only one sorus on each pinna.{{sfn|Crouch|Klopper|Burrows|Burrows|2011|p=612}}

Among the larger ferns, ''A.&nbsp;platyneuron'' might be confused with a young Christmas fern, ''[[Polystichum acrostichoides]]'', but that species is generally much larger and has a green, scaly stipe and rachis.{{sfn|Cobb|Farnsworth|Lowe|2005|p=70}} Fishbone fern, ''[[Nephrolepis cordifolia]]'', is likewise larger, with yellowish-green pinnae and a green rachis.{{sfn|Crouch|Klopper|Burrows|Burrows|2011|p=612}}

==Taxonomy==
This species is commonly known as "ebony spleenwort"{{sfn|Cobb|Farnsworth|Lowe|2005|p=70}} or "brownstem spleenwort" for the dark color of its stipe and rachis.{{sfn|Snyder|Bruce|1986|p=86}}

The [[basionym]] for the species is ''Acrostichum platyneuros'', published by [[Carl Linnaeus|Linnaeus]] in ''[[Species Plantarum]]'' in 1753 (the official starting point of modern botanical nomenclature).{{sfn|Linnaeus|1753|pp=1069–1070}} Linnaeus' treatment came from a 1745 dissertation by his student J. B. Heiligtag, which in turn drew on the descriptions by several earlier authorities.{{sfn|Fernald|1935|pp=382–383}} The first description listed was that of [[Jan Frederik Gronovius|Jan Gronovius]], botanist and mentor of Linnaeus, in his ''Flora Virginica'' of 1743, based on a specimen collected by the collector [[John Clayton (botanist)|John Clayton]].{{sfn|Linnaeus|1753|pp=1069–1070}} The specific epithet ''platyneuros'' ("flat nerves") was drawn from a description by the botanist [[Leonard Plukenet]] in his ''Almagestum'' of 1696.{{efn|The description read "Filix Polypodium dicta minima virginiana platyneuros".}} Unfortunately, only Clayton's specimen, now the [[lectotype]] for the species, represents the species now known as ''Asplenium&nbsp;platyneuron''; the specimens upon which the other descriptions are based, including that of Plukenet which yielded the specific epithet, are a mixture of ''[[Pleopeltis polypodioides]]'' and ''[[Polypodium virginianum]]'' ''[[sensu lato]]''.{{sfn|Fernald|1935|p=383}} In 1789, the species was independently described by [[William Aiton]] in ''[[Hortus Kewensis]]'', and given the name ''Asplenium ebeneum'',{{sfn|Aiton|1789|p=462}} referring to the [[ebony]] color of its stalk.{{sfn|Lowe|1869|p=169}} The species was also independently described by [[Olof Swartz]] in 1801, as ''Asplenium polypodioides'',{{sfn|Swartz|1801|p=53}} and by [[André Michaux]] in 1803 as ''Asplenium trichomanoides'';{{sfn|Michaux|1803|p=265}} both these names were reduced to synonymy with ''Asplenium ebeneum'' by [[Carl Ludwig Willdenow]].{{sfn|Willdenow|1810|p=329}} The name ''Asplenium trichomanoides'', however, had already been used by Linnaeus in 1767, making Michaux's name a ''[[nomen illegitimum]]''.{{sfn|Tropicos|2013}}

It was Aiton's epithet, ''ebeneum'', that was used by American botanists throughout most of the 19th century.{{sfn|Lellinger|1981|p=90}} The transfer of Linnaeus' specific epithet to form the name ''Asplenium platyneuron'' was mooted by [[Daniel Cady Eaton|D. C. Eaton]] in 1878, who attributed the combination to a pencil notation by William Oakes in the margin of a copy of ''Flora Virginica''.{{sfn|Eaton|1878|p=21}} Therefore, the combination has historically been attributed to Oakes or Oakes ex D.C.Eaton. However, in 1981, David B. Lellinger pointed out that Eaton had not, in fact, accepted the combination in 1878, preferring the more descriptive epithet ''ebeneum'' to the less accurate through senior ''platyneuron''. Eaton's use, therefore, was to be treated as provisional, and not as a published combination by him.{{sfn|Lellinger|1981|p=90}} Eaton aside, the first valid publication of ''Asplenium platyneuron'' was that of [[Nathaniel Lord Britton|Britton]], Emerson E. Sterns, and [[Justus Ferdinand Poggenburg I|Justus F. Poggenburg]] in 1888, which implicitly references Linnaeus's basionym.{{sfn|Britton|Sterns|Poggenburg|1888|p=73}} Despite the revival of Linnaeus' epithet, the name ''Asplenium ebeneum'' continued to be widely used through 1896, when [[Lucien Underwood]], in Britton & Brown's ''Illustrated Flora'', used the name ''Asplenium platyneuron'' with explicit reference to the basionym.{{sfn|Britton|Brown|1896|p=23}}

The species has twice been placed in genera segregated from ''[[Asplenium]]'': as ''Chamaefilix platyneuros'' by [[Oliver Atkins Farwell|Oliver A. Farwell]] in 1931,{{sfn|Farwell|1931|p=269}} and as ''Tarachia platyneura'' by Sizuo Momose in 1960.{{sfn|Momose|1960}} Neither combination was widely accepted and current authorities do not recognize these genera.{{sfn|Wagner|Moran|Werth|1993}}

A global phylogeny of ''Asplenium'' published in 2020 divided the genus into eleven clades,{{sfn|Xu|Zhang|Rothfels|Smith|2020|p=27}} which were given informal names pending further taxonomic study. ''A.&nbsp;platyneuron'' belongs to the "''A.&nbsp;incisum'' subclade" of the "''Schaffneria'' clade".{{sfn|Xu|Zhang|Rothfels|Smith|2020|p=36}} The ''Schaffneria'' clade has a worldwide distribution, and members vary widely in form and habitat.{{sfn|Xu|Zhang|Rothfels|Smith|2020|p=42}} There is no clear morphological feature that has evolved within the ''A.&nbsp;incisum'' subclade to define it, but members of the subclade do share a chestnut-brown stipe base. Relationships within the clade are not well-resolved;{{sfn|Xu|Zhang|Rothfels|Smith|2020|p=43}} it includes species from South America, Europe, and China, but no other North American species.{{sfn|Xu|Zhang|Rothfels|Smith|2020|p=36}}

===Forms and varieties===
Three varieties were recognized by Carl Taylor ''et al.'' in 1976 in their treatment of the species: ''A.&nbsp;platyneuron'' var.&nbsp;''platyneuron'', the typical variety, ''A.&nbsp;platyneuron'' var.&nbsp;''incisum'', with more deeply cut pinnae, and ''A.&nbsp;platyneuron'' var.&nbsp;''bacculum-rubrum'', larger and more fertile than the others with toothed pinnae. However, they note that both these varieties intergrade,{{sfn|Taylor|Mohlenbrock|Burton|1976|p=63}} and ''Flora of North America'' does not recognize any infraspecific taxa.{{sfn|Wagner|Moran|Werth|1993}}{{efn|''A.&nbsp;platyneuron'' var.&nbsp;''bacculum-rubrum'' (Featherm.) Fernald is erroneously referred to as ''A.&nbsp;platyneuron'' f.&nbsp;''bacculum-rubrum'' (Fernald) Fernald in the ''Flora of North America'' synonymy.}} <!-- Weakley's draft flora also suggests they not be recognized. --> In addition to these varieties, three [[form (botany)|form]]s were recognized by Taylor ''et al.''{{sfn|Taylor|Mohlenbrock|Burton|1976|p=63}} ''A.&nbsp;platyneuron'' f.&nbsp;''proliferum'', discussed below, is not recognized by later treatments.{{sfn|Wagner|Johnson|1981|p=164}}{{sfn|Wagner|Moran|Werth|1993}} ''A.&nbsp;platyneuron'' f.&nbsp;''hortonae'' is only known from sporadic, sterile specimens, with pinnae imbricate and deeply cut and lobed. In ''A.&nbsp;platyneuron'' f.&nbsp;''furcatum'', the rachis is multiply branched near the tip, but the form appears otherwise normal.{{sfn|Taylor|Mohlenbrock|Burton|1976}}

''Asplenium ebeneum'' var.&nbsp;''bacculum-rubrum'' was first described in 1871 by Americus Featherman. His epithet refers to [[Baton Rouge, Louisiana]], where he found it growing at the edges of cultivated fields and [[canebrake]]s. He described it as standing from {{convert|1|to|2|ft|m|sigfig=1|sp=us}} high, with twenty to thirty "elongated" sori on each pinna.{{sfn|Featherman|1871|p=75}} A large variety of ''Asplenium platyneuron'' found throughout the southeastern United States, with distinct rather than confluent sori, was described by [[M. L. Fernald]] in 1935 as ''Asplenium platyneuron'' var.&nbsp;''euroaustrinum'', who was then unaware of Featherman's publication.{{sfn|Fernald|1935|p=382}} He subsequently deemed the two to be identical, and transferred Featherman's variety to ''A.&nbsp;platyneuron'', as ''A.&nbsp;platyneuron'' var.&nbsp;''bacculum-rubrum'', in 1936.{{sfn|Fernald|1936}} According to Taylor ''et al.'', this variety may be recognized by a longest pinna length greater than {{convert|3.5|cm|in|sp=us}} and the almost universal presence of sori on erect fronds.{{sfn|Taylor|Mohlenbrock|Burton|1976|p=63}} They described it as bearing fertile fronds up to {{convert|70|cm|in|sp=us}}, with as many as seventy pinnae, and a coarse appearance with roughly toothed leaf edges intergrading with ''A.&nbsp;platyneuron'' var.&nbsp;''incisum''.{{sfn|Taylor|Mohlenbrock|Burton|1976|p=67}} [[Warren H. Wagner|Herb Wagner]] and David M. Johnson, who collected similar material in [[Cass County, Michigan]] (well to the northwest of the supposed range of the variety) did not consider morphological variation in var.&nbsp;''bacculum-rubrum'' to be distinct from typical material except for its size, and recommended it be given taxonomic status no higher than that of a form, if recognized at all.{{sfn|Wagner|Johnson|1981|pp=164–165}}

''Asplenium ebeneum'' var.&nbsp;''incisum'' was collected by [[Elliot C. Howe]] in [[Poestenkill, New York]] and described in 1869 by [[Charles Horton Peck|Charles H. Peck]]. Although described as having pinnae largely "incised-pinnatifid",{{sfn|Peck|1869|p=104}} most of the pinnae in the type material are doubly serrate (toothed) or serrate-incised.{{sfn|Taylor|Mohlenbrock|Burton|1976|p=65}} In 1873, Elihu S. Miller collected fronds from [[Wading River, New York]] which were wider than usual and sharply serrate. This he named ''Asplenium ebeneum'' var.&nbsp;''serratum'', at the suggestion of [[Asa Gray]].{{sfn|Miller|1873|p=41}}{{efn|Older literature often attributes the epithet to Gray, rather than Miller.}} Although Miller's type material has not been located, specimens determined as var.&nbsp;''serratum'' by Gray were found by Taylor ''et al.'' to be indistinguishable from var.&nbsp;''incisum''.{{sfn|Taylor|Mohlenbrock|Burton|1976|p=65}} However, both epithets continued to be recognized by authors for some time. Britton, Sterns and Poggenburg transferred var.&nbsp;''serratum'' as ''A.&nbsp;platyneuron'' var.&nbsp;''serratum'' in 1888;{{sfn|Britton|Sterns|Poggenburg|1888|p=73}} [[Willard Nelson Clute|Willard Clute]] lowered its rank to become ''A.&nbsp;ebeneum'' f.&nbsp;''serratum'' in 1901,{{sfn|Clute|1901|p=314}} and the combination at this rank was transferred to ''A.&nbsp;platyneuron'' by [[Ralph Hoffmann]] in 1922.{{sfn|Hoffmann|1922|p=193}} [[Benjamin Lincoln Robinson]] transferred var.&nbsp;''incisum'' to ''A.&nbsp;platyneuron'' in 1908,{{sfn|Robinson|1908|p=29}} and Farwell recognized var.&nbsp;''serratum'' when he segregated ''Chamaefilix'' from ''Asplenium'' in 1931.{{sfn|Farwell|1931|p=270}} [[Edgar T. Wherry]], in 1940, synonymized not only var.&nbsp;''serratum'' with var.&nbsp;''incisum'', but included var.&nbsp;''bacculum-rubrum'' and var.&nbsp;''euroaustrinum'' under that epithet. He also created the epithet var.&nbsp;''typicum'' for the normal form of ebony spleenwort.{{sfn|Wherry|1940|p=14}} Taylor ''et al.'', reviewing these treatments, distinguished var.&nbsp;''incisum'' as having doubly serrate pinnae cut less than 80% of the way to the costa, with normal fertility (unlike the sterile ''A.&nbsp;platyneuron'' f.&nbsp;''hortonae'').{{sfn|Taylor|Mohlenbrock|Burton|1976|p=65}} As these plants occur throughout the range of the species intermixed with typical specimens and intergrading with them morphologically, Wagner and Johnson did not think them worth of taxonomic recognition.{{sfn|Wagner|Johnson|1981|p=164}}

Another taxon characterized by deeply incised margins was described in 1901 by [[George E. Davenport]] as ''Asplenium ebeneum'' var.&nbsp;''hortonae''. These specimens were found in 1900 growing on [[limestone]] in [[Brattleboro, Vermont]] by Frances B. Horton, for whom Davenport named the variety. In this variety, all the pinnae (including the more reduced basal pinnae) are obliquely toothed or cut very nearly into separate, toothed pinnules. The upright fronds are sterile.{{sfn|Davenport|1901}} Willard Clute treated it as a form, ''A.&nbsp;ebeneum'' f.&nbsp;''hortonae'', in 1906.{{sfn|Clute|1906|p=86}} B. L. Robinson, in 1908, declared ''A.&nbsp;ebeneum'' var.&nbsp;''hortonae'' a synonym of ''A.&nbsp;platyneuron'' var.&nbsp;''incisum''.{{sfn|Robinson|1908|p=30}} Clute transferred the epithet at the varietal level to form ''A.&nbsp;platyneuron'' var.&nbsp;''hortonae'' in 1909, but he also equated this with var.&nbsp;''incisum''.{{sfn|Clute|1909|p=21}} [[Lyman Bradford Smith|Lyman B. Smith]] continued to recognize it in [[Massachusetts]], treating it as the form ''A.&nbsp;platyneuron'' f.&nbsp;''hortonae'' in 1928.{{sfn|Smith|1928|p=14}} In 1937, Arthur Leeds explicitly distinguished it at varietal level, noting that a photograph of the type of ''A.&nbsp;ebeneum'' var.&nbsp;''incisum'' did not closely correspond to ''A.&nbsp;ebeneum'' var.&nbsp;''hortonae'', having merely toothed rather than deeply cut and overlapping pinnae.{{sfn|Leeds|1937}} Edgar Wherry also explicitly distinguished ''A.&nbsp;platyneuron'' var.&nbsp;''hortonae'' from ''A.&nbsp;platyneuron'' var.&nbsp;''incisum'', erroneously duplicating Clute's 1909 combination.{{sfn|Wherry|1940|p=14}} Material collected from [[St. Mary's County, Maryland]] was described by James E. Benedict, Jr. in 1947 as ''A.&nbsp;platyneuron'' f.&nbsp;''dissectum'', noting that while similar to f.&nbsp;''hortonae'', some of the pinnae in his material were completely cut into pinnules, which were themselves deeply lobed.{{sfn|Benedict|1947}} Taylor ''et al.'' noted that much of Benedict's material, however, resembled typical f.&nbsp;''hortonae'', although approaching var.&nbsp;''bacculum-rubrum'' in size. They equated f.&nbsp;''dissectum'' with f.&nbsp;''hortonae'', and noted that specimens of the latter could approach var.&nbsp;''incisum'' and var.&nbsp;''bacculum-rubrum''.{{sfn|Taylor|Mohlenbrock|Burton|1976|pp=66–67}} While Wagner and Johnson declined to distinguish most infraspecific taxa within ''A.&nbsp;platyneuron'', they did recognize f.&nbsp;''hortonae'' as a "rare sterile form".{{sfn|Wagner|Johnson|1981|p=164}}

A form with forked fronds was known around the end of the nineteenth century, and was formally described in 1909 by Willard Clute as ''A.&nbsp;platyneuron'' f.&nbsp;''furcatum''. The form differs from normal ''A.&nbsp;platyneuron'' only in forking near the apex of the blade.{{sfn|Clute|1909b}} Robert M. Tetrick II discovered similar plants in [[West Virginia]], which he described as having "fronds much branched, the ultimate divisions crested" and named ''A.&nbsp;platyneuron'' f.&nbsp;''multifidum''.{{sfn|Tetrick|1949}} Taylor ''et al.'' compared the type of this form with Clute's illustration of f.&nbsp;''furcatum'' and considered them to be the same.{{sfn|Taylor|Mohlenbrock|Burton|1976|pp=67–68}} Wagner & Johnson noted that such forms were a frequent developmental error in many species of North American fern.{{sfn|Wagner|Johnson|1981|p=164}}

The formation of proliferating buds in ebony spleenwort has also given rise to a taxonomic distinction. Bud formation was first observed by the nurseryman Conrad [[Loddiges]] in 1817, in specimens in cultivation in [[Great Britain]].{{sfn|Loddiges|1817|loc=Pl. 5}} However, the phenomenon was overlooked{{sfn|Weatherby|1924}} until 1879, when D. C. Eaton observed it in specimens from [[Florida]]. He took this for an aberrant [[variety (botany)|variety]], which he named ''A.&nbsp;ebeneum'' var.&nbsp;''proliferum''.{{sfn|Eaton|1879|p=307}} Willard Clute reduced its status from a variety to a [[form (botany)|form]], ''A.&nbsp;ebeneum'' f.&nbsp;''proliferum'', in 1906.{{sfn|Clute|1906|p=86}} Similar specimens were subsequently reported from Maryland, Pennsylvania, and Connecticut; the buds appeared on the rachis of sterile fronds, and were often only detected when mounting the specimen.{{sfn|Waters|1903}}{{sfn|Waters|1904}}{{sfn|Marshall|1923}} In 1924, Frederick G. Floyd argued that the formation of these proliferations was a normal characteristic of the species, which appeared regularly, if not universally, and did not warrant a varietal designation. He also observed the formation of proliferating buds on a fertile rachis of ''A.&nbsp;ebeneum'' var.&nbsp;''serratum''.{{sfn|Floyd|1924}} Floyd's position was not universally accepted: Louise Tanger made a new combination for the form, ''A.&nbsp;platyneuron'' f.&nbsp;''proliferum'' in 1933,{{sfn|Tanger|1933|p=16}} and Taylor ''et al.'' recognized it in a discussion of infraspecific taxa in the species in 1976. However, these authors noted that specimens of ''A.&nbsp;platyneuron'' f.&nbsp;''proliferum'' would be assigned to various other varieties if they were not proliferous.{{sfn|Taylor|Mohlenbrock|Burton|1976|p=68}} Wagner & Johnson, in 1981, declined to recognize the taxon on grounds similar to Floyd's,{{sfn|Wagner|Johnson|1981|p=164}} and Wagner's treatment in ''Flora of North America'' does not mention the form.{{sfn|Wagner|Moran|Werth|1993}}

===Hybrids===
As part of the "Appalachian ''Asplenium'' complex", ebony spleenwort has been found to form hybrids with a number of other spleenworts. The hybrid with mountain spleenwort ([[Asplenium montanum|''A.&nbsp;montanum'']]) has been collected only rarely, but on multiple occasions, this hybrid has undergone chromosome doubling to give rise to the fertile species known as Bradley's spleenwort ([[Asplenium bradleyi|''A.&nbsp;bradleyi'']]).{{sfn|Wagner|1954}}{{sfn|Werth|Guttman|Eshbaugh|1985}} A backcross between ''A.&nbsp;bradleyi'' and ''A.&nbsp;platyneuron'' is believed to have been collected twice, from a now-destroyed site in Pennsylvania,{{sfn|Wherry|1940|p=24}} and in a preliminary report from [[Sequatchie County, Tennessee]].{{sfn|Evans|1989|p=105}} The hybrid with walking fern ([[Asplenium rhizophyllum|''A.&nbsp;rhizophyllum'']]), known as Scott's spleenwort ([[Asplenium × ebenoides|''A.&nbsp;×&nbsp;ebenoides'']]), regularly appears where the two parent species grow together. At one locality, in Havana Glen, Alabama, ''A.&nbsp;×&nbsp;ebenoides'' has undergone chromosome doubling to produce a fertile species, Tutwiler's spleenwort ([[Asplenium tutwilerae|''A.&nbsp;tutwilerae'']]).{{sfn|Wagner|1954}} The backcross between ''A.&nbsp;platyneuron'' and ''A.&nbsp;tutwilerae'' is known as Boydston's spleenwort ([[Asplenium × boydstoniae|''A.&nbsp;×&nbsp;boydstoniae'']]), occurring in nature only with ''A.&nbsp;tutwilerae'' at Havana Glen.{{sfn|Walter|Wagner|Wagner|1982|p=73}} ''A.&nbsp;platyneuron'' is also known to hybridize with lobed spleenwort ([[Asplenium pinnatifidum|''A.&nbsp;pinnatifidum'']]), a descendant of mountain spleenwort and walking fern, to produce the rare Kentucky spleenwort ([[Asplenium × kentuckiense|''A.&nbsp;×&nbsp;kentuckiense'']]).{{sfn|Smith|Bryant|Tate|1961}} Evidence for these hybridizations was obtained through cytological studies,{{sfn|Wagner|1954}} [[chromatography]],{{sfn|Smith|Levin|1963}} and [[allozyme]] [[electrophoresis]].{{sfn|Werth|Guttman|Eshbaugh|1985}}

Outside of the "Appalachian ''Asplenium'' complex", ''A.&nbsp;platyneuron'' can also hybridize with wall-rue ([[Asplenium ruta-muraria|''A.&nbsp;ruta-muraria'']]), forming Morgan's spleenwort ([[Asplenium × morganii|''A.&nbsp;×&nbsp;morganii'']]), and with maidenhair spleenwort ([[Asplenium trichomanes|''A.&nbsp;trichomanes'']]) to form Virginia spleenwort ([[Asplenium × virginicum|''A.&nbsp;×&nbsp;virginicum'']]). ''A.&nbsp;×&nbsp;morganii'' is known from one specimen, collected from a limestone cliff overlooking the [[Potomac River]] in Maryland,{{sfn|Wagner|Wagner|1990|p=44}} while ''A.&nbsp;×&nbsp;virginicum'' has been collected three times, from Pennsylvania,{{sfn|Correll|1939|p=102}} Virginia,{{sfn|Maxon|1938|pp=141–142}} and North Carolina. A hybrid with Asian walking fern, [[Asplenium ruprechtii|''A.&nbsp;ruprechtii'']], has been produced in cultivation and is informally known as [[Asplenium × crucibuli|''A.&nbsp;×&nbsp;crucibuli'']] in horticulture. It is similar to ''A.&nbsp;×&nbsp;ebenoides'', but the frond is linear in shape, rather than being wider at the base.{{sfn|Hoshizaki|Moran|2001|p=197}}

==Distribution and habitat==
In North America, ''A.&nbsp;platyneuron'' is native throughout the eastern United States from southern Maine to the southeastern corner of Wisconsin, south to Florida and west to eastern Nebraska, Kansas, Oklahoma, and Texas, and in the far southeast of Canada. It is also found around the meeting point of Colorado, New Mexico, and Oklahoma, and in isolated small populations in New Mexico, Arizona and the [[West Indies]].{{sfn|Kartesz|2014}} Outside of North America, ''A.&nbsp;platyneuron'' is found in tropical and subtropical southern Africa, a distribution not known for any other North American fern.{{sfn|Wagner|Moran|Werth|1993}} It ranges from the [[Western Cape]] province of [[South Africa]] northwards along the eastern seaboard to [[Gauteng]] and [[Mpumalanga]] provinces, its distribution including [[Lesotho]].{{sfn|Crouch|Klopper|Burrows|Burrows|2011|p=612}} An isolated population was found on [[serpentine soil]] in an [[oak]] woodland in [[Slovakia]] in 2009.{{sfn|Ekrt|Hrivnák|2010|p=358}} Since the 1960s, ''A.&nbsp;platyneuron'' has spread rapidly and aggressively in the [[Great Lakes]] region, where it was formerly uncommon.{{sfn|Wagner|Johnson|1981|p=156}} Though widespread in southern Africa, it is not particularly abundant, and in that part of its range is most commonly found in Lesotho.{{sfn|Crouch|Klopper|Burrows|Burrows|2011|p=612}}

''Asplenium platyneuron'' can be found in a wide variety of habitats, at altitudes from {{convert|0|to|1300|m|ft|sp=us|-2}}.{{sfn|Wagner|Moran|Werth|1993}} It will tolerate soils ranging from {{not a typo|mediacid}} ([[pH]] 3.5–4.0) to subalkaline (pH 8.0–8.5),{{sfn|Wherry|1920b|p=259}} although it prefers subacid soils (pH 4.5–5.0) over {{not a typo|mediacid}}.{{sfn|Wherry|1920|pp=45–46}} Unlike many other North American spleenworts, it can grow on soil as well as rock.{{sfn|Wagner|Johnson|1981|p=158}} When growing in soil, it can be found in forests and woodlands,{{sfn|Weakley|2015|p=87}} including sandy pinelands,{{sfn|Lady Bird Johnson Wildflower Center}} as well as [[old field (ecology)|old field]]s{{sfn|Weakley|2015|p=87}} and other disturbed sites. It can colonize a variety of rocks,{{sfn|Wagner|Moran|Werth|1993}} particularly (but not limited to){{sfn|Wagner|Johnson|1981|p=158}} [[calcareous]] ones, and will also grow on [[Mortar (masonry)|mortared]] walls.{{sfn|Weakley|2015|p=87}} In South Africa, it is generally found at altitudes over 600&nbsp;meters (2,000&nbsp;ft), in habitats similar to those it prefers in North America (under small bushes and on rocky banks).{{sfn|Sim|1915|p=141}} It typically occurs neither in full shade nor in full sun, but at the base of rocks in grasslands and at forest edges and in ''[[Leucosidea]]'' scrub.{{sfn|Crouch|Klopper|Burrows|Burrows|2011|p=612}}

==Ecology and conservation==
Protein extracts from ''A.&nbsp;platyneuron'' have been shown to deter insect predation on [[soybean]]s to a significant extent,{{sfn|Markham|Chalk|Stewart|2006|p=116}} and the [[Missouri Botanical Garden]] describes it as lacking "serious insect or disease problems".{{sfn|Missouri Botanical Garden}} However, a population of several hundred individuals in Florida was reported to have been almost wiped out by insect activity.{{sfn|Satchwell|1916|p=41}} It is susceptible to slugs.{{sfn|Missouri Botanical Garden}} The black fern aphid (''[[Idiopterus nephrelepidis]]'') can feed on it.{{sfn|Robinson|1966}}

[[Sporophyte]]s are fairly tolerant of drought, but require well-drained soils.{{sfn|Lady Bird Johnson Wildflower Center}}{{sfn|Missouri Botanical Garden}} The [[prothallia]] ([[gametophyte]]s) of ''A.&nbsp;platyneuron'' can survive periods of drought for up to a month. There is some evidence to show that the prothallia may undergo clonal reproduction and fission, which has been induced in the laboratory through variations in light intensity.{{sfn|Pickett|1931|pp=54–55}}

A variety of adaptations make ''A.&nbsp;platyneuron'' an aggressive colonizer, even weedy, when compared with other spleenworts, although a warming climate and an increase in [[secondary forest|second growth]] habitats may also have played a role in its expansion in the Great Lakes region. It tolerates broad variation in soil conditions, including [[pH]], and will grow in both sun and shade.{{sfn|Wagner|Johnson|1981|p=158}} The starchy stipe bases provide energy for rapid growth in the spring, allowing the fronds to keep ahead of competing vegetation. The erect fertile fronds, unusual for ''Asplenium'', help release spores into the wind for long-distance dispersal, while the proliferative buds allow clonal propagation in moist, fertile habitats.{{sfn|Wagner|Johnson|1981|p=164}} The species also carries a very low [[genetic load]], so that viable sporophytes can develop from intragametophytic self-fertilization with 83–89% success. This means that new sporophytes can usually grow from the gametophyte formed from a single spore. This has allowed ebony spleenwort to be an early colonizer, from distant locations, of recently disturbed habitats, such as [[spoil tip|coal spoils]] in southern [[Iowa]].{{sfn|Crist|Farrar|1983}} The appearance of ''A.&nbsp;platyneuron'' in a disturbed habitat in Slovakia, {{convert|6500|km|mi|sp=us|sigfig=2}} from the nearest known sites in eastern North America, is probably the result of long-distance dispersal, which may also have allowed it to colonize and naturalize in South Africa.{{sfn|Ekrt|Hrivnák|2010|p=361}}

While globally secure (G5), ebony spleenwort is considered an [[endangered species]] in some of the [[U.S. state|state]]s and [[Provinces and territories of Canada|province]]s at the northern and western edges of its North American range. [[NatureServe]] considers it to be critically imperiled (S1) in Arizona and Colorado, imperiled (S2) in Nebraska, Maine, Rhode Island, and Quebec, and vulnerable (S3) in Florida and Minnesota.{{sfn|NatureServe|2024}}

==Cultivation==
The ebony spleenwort is sometimes grown as a [[terrarium]] or [[garden]] plant. It can be cultivated in sandy [[peat]],{{sfn|Loddiges|1817|loc=Pl. 5}} subacid garden soil,{{sfn|Lellinger|1985|p=241}} other gravelly, sandy{{sfn|Lady Bird Johnson Wildflower Center}} or gritty soils,{{sfn|Missouri Botanical Garden}} or [[potting mix]] under moist to dry conditions.{{sfn|Hoshizaki|Moran|2001|p=202}} Both acid and alkaline soils are acceptable.{{sfn|Lady Bird Johnson Wildflower Center}} Good drainage is essential, and the species will grow even in dry soil.{{sfn|Lady Bird Johnson Wildflower Center}}{{sfn|Missouri Botanical Garden}} Partial sun{{sfn|Lellinger|1985|p=241}} or low to high light is recommended,{{sfn|Hoshizaki|Moran|2001|p=202}} although full shade is tolerated.{{sfn|Missouri Botanical Garden}} Plants are said to be easy to maintain once they have become established,{{sfn|Hoshizaki|Moran|2001|p=202}} but it has been described as "rather difficult" to grow in [[Germany]].{{sfn|Ekrt|Hrivnák|2010|p=362}} Conrad Loddiges found it necessary to use artificial heat to cultivate ebony spleenwort in Great Britain.{{sfn|Loddiges|1817|loc=Pl. 5}}

==See also==
*[[Asplenium hybrids]]

==Notes and references==
===Notes===
{{notelist}}

===References===
{{Reflist|3}}

===Works cited===
{{refbegin|2}}
*{{cite book | title=Hortus Kewensis | volume=3 | year=1789 | last=Aiton | first=William | author-link=William Aiton | publisher=George Nicol | location=London | url=https://www.biodiversitylibrary.org/page/5875222}}
*{{cite journal |title=Spore Morphology of the Polypodiaceae of Northeastern North America. II. |last1=Belling |first1=Alice J. |last2=Heusser |first2=Calvin J. |journal=Bulletin of the Torrey Botanical Club |volume=102 |issue=3 |year=1975 |pages=115–127 |doi=10.2307/2484733 |jstor=2484733}}
*{{cite journal | title=A new form of Asplenium platyneuron | last=Benedict | first=J. E. | year=1947 | journal=[[American Fern Journal]] | volume=37 | issue=1 | pages=11–12 | doi=10.2307/1545333 |jstor=1545333 | url=https://www.biodiversitylibrary.org/page/32411638}}
*{{cite book | last1=Britton | first1=N. L. | authorlink1=Nathaniel Lord Britton | last2=Brown | first2=Addison | authorlink2=Addison Brown | title=An illustrated flora of the northern United States, Canada and the British Possessions From Newfoundland to the Parallel of the Southern Boundary of Virginia, and from the Atlantic Ocean Westward to the 102d Meridian | volume=I | year=1896 | publisher=[[Charles Scribner's Sons]] | location=New York}}
*{{cite book | title=Preliminary catalog of Anthophyta and Pteridophyta, reported as growing spontaneously within one hundred miles of New York City | year=1888 | last1=Britton | first1=N. L. | last2=Sterns | first2=E. E. | last3=Poggenburg | first3=Justus F. | authorlink3=Justus Ferdinand Poggenburg I | location=New York |publisher=Torrey Botanical Club | url=http://webdev.archive.org/details/preliminarycatal00torr}}
*{{cite book | title=Our Ferns in their Haunts | last=Clute | first=Willard Nelson | author-link=Willard Nelson Clute | others=Illustrated by William Walworth Stilson | publisher=Frederick A. Stokes Company | location=New York | year=1901 | url=https://www.biodiversitylibrary.org/page/23984098 | doi=10.5962/bhl.title.33037}}
*{{cite journal | title=A checklist of the North American fernworts (continued) | last=Clute | first=Willard N. | year=1906 | volume=14 | issue=3 | journal=Fern Bulletin | pages=86–90 | url=http://catalog.hathitrust.org/Record/000549002}}
*{{cite journal | title=More additions to the checklist | last=Clute | first=Willard N. | year=1909 | journal=Fern Bulletin | volume=17 | issue=1 | pages=20–21 | url=http://catalog.hathitrust.org/Record/000549002}}
*{{cite journal | title=Rare Forms of Ferns-XI | last=Clute | first=Willard N. | year=1909b | journal=Fern Bulletin | volume=17 | issue=3 | pages=88–89 | url=http://catalog.hathitrust.org/Record/000549002}}
*{{cite book | title=A Field Guide to Ferns of Northeastern and Central North America | first1=Boughton | last1=Cobb | first2=Elizabeth | last2=Farnsworth | first3=Cheryl | last3=Lowe | publisher=Houghton Mifflin | location=New York City | year=2005 | series=Peterson Field Guides | isbn=0-618-39406-0}}
*{{cite journal | last=Correll | first=Donovan S. | title=Some fern notes | journal=American Fern Journal | volume=29 | issue=3 | pages=102–105 | year=1939 | url=https://www.biodiversitylibrary.org/page/32262916 | doi=10.2307/1545572 |jstor=1545572}}
*{{cite journal | title=Genetic load and long-distance dispersal in ''Asplenium platyneuron'' | last1=Crist | first1=Kathryn Carvey | last2=Farrar | first2=Donald R. | year=1983 | journal=Canadian Journal of Botany | volume=61 | issue=6 | pages=1809–1814 | doi=10.1139/b83-190}}
*{{cite book |title=Ferns of Southern Africa |last1=Crouch |first1=Neil R |last2=Klopper |first2=Ronell R |last3=Burrows |first3=John E |last4=Burrows |first4=Sandra M | year=2011 |publisher=Struik Nature |location=Cape Town, South Africa |isbn=978-1-77007-910-6}}
*{{cite journal | title=A plumose variety of the ebony spleenwort | last=Davenport | first=George E. | year=1901 | journal=[[Rhodora (journal)|Rhodora]] | volume=3 | issue=25 | pages=1–2 | url=https://www.biodiversitylibrary.org/page/560561 |jstor=23293237}}
*{{cite book |title=The Ferns and Lycophytes of Texas |last1=Diggs |first1=George M. Jr. |last2=Lipscomb |first2=Barney L. |publisher=Botanical Research Institute of Texas Press |location=Fort Worth, Texas |year=2014 |isbn=978-1-889878-37-9}}
*{{cite book | title=The Ferns of North America | last=Eaton | first=D. C. | author-link=Daniel Cady Eaton | volume=1 pt. 2 | publisher=B. Whidden | location=Boston, Massachusetts | year=1878}}
*{{cite journal | title=New or little-known ferns of the United States | last=Eaton | first=D. C. | journal=Bulletin of the Torrey Botanical Club | year=1879 | volume=6 | issue=52 | pages=306–307 | url=https://www.biodiversitylibrary.org/page/646942 | doi=10.2307/2476818 |jstor=2476818}}
*{{cite journal |last=Evans |first=A. Murray |title=The ferns and fern allies of Tennessee: an update |journal=Journal of the Tennessee Academy of Science |volume=64 |issue=3 |year=1989 |pages=103–105 |url=http://iweb.tntech.edu/sstedman/JTAS%2064-3-pt1.pdf }}{{dead link|date=July 2017 |bot=InternetArchiveBot |fix-attempted=yes }}
*{{cite journal |last1=Ekrt | first1=Libor | last2=Hrivnák | first2=Richard | title=''Asplenium platyneuron'', a new pteridophyte for Europe | journal=Preslia | volume=82 | year=2010 | pages=357–364 | url=http://ibot.sav.sk/usr/Richard/docs/EkrtHrivnak_Preslia_Asplenium_platyneuron_2010.pdf}}
*{{cite journal | title=Fern Notes II. Ferns in the Herbarium of Parke, Davis & co | year=1931 | last=Farwell | first=Oliver Atkins | author-link=Oliver Atkins Farwell | journal=[[American Midland Naturalist]] | volume=12 | issue=8 | pages=233–311 | doi=10.2307/2420088 |jstor=2420088}}
*{{cite book | last=Featherman | first=Americus | year=1871 | title=Report of botanical survey of southern and central Louisiana made during the year 1870 | publisher=Office of the Republican | location=New Orleans | url=https://archive.org/details/reportla00feat}}
*{{cite journal | title=Midsummer vascular plants of Virginia | last=Fernald | first=M. L. | author-link=Merritt Lyndon Fernald | year=1935 | journal=Rhodora | volume=37 | issue=442 | pages=378–413 | url=https://www.biodiversitylibrary.org/page/604464 |jstor=41764202}}
*{{cite journal | title=''Asplenium platyneuron'' (L.) Oakes, var. ''bacculum-rubrum'' (Featherman), comb. nov. | last=Fernald | first=M. L. | year=1936 | journal=Rhodora | volume=38 | issue=453 | page=304 | url=https://www.biodiversitylibrary.org/page/605094 |jstor=23300856}}
*{{cite journal | title=Proliferation of ''Asplenium platyneuron'' (L.) Oakes | last=Floyd | first=F. G. | year=1924 | journal=American Fern Journal | volume=14 | issue=1 | pages=13–17 | url=https://www.biodiversitylibrary.org/page/30823937 | doi=10.2307/1544373 |jstor=1544373}}
*{{cite book | first1=Barbara Joe | last1=Hoshizaki | first2=Robbin C. | last2=Moran | title=Fern Grower's Manual | year=2001 | publisher=Timber Press | location=Portland, Oregon | isbn=9780881924954}}
*{{cite journal | title=Flora of Berkshire County, Massachusetts | last=Hoffmann | first=Ralph | author-link=Ralph Hoffmann | year=1922 | journal=Proceedings of the Boston Society of Natural History | volume=36 | issue=5 | pages=171–382 | url=https://www.biodiversitylibrary.org/page/37606858 | doi=10.5962/bhl.title.55096| hdl=2027/coo.31924001690514 | hdl-access=free }}
*{{cite web | first=John T. | last=Kartesz | title=''Asplenium'' | work=Biota of North America Program | year=2014 | url=http://bonap.net/NAPA/TaxonMaps/Genus/County/Asplenium}}
*{{citation | last=Kinder | first=Lois A. | title=A study of ''Asplenium platyneuron'' (L.) Oakes and ''Camptosorus rhizophyllus'' (L.) Link with an emphasis on spore morphology | year=1966 | type=thesis | url=http://cardinalscholar.bsu.edu/handle/handle/191142}}
*{{cite web | ref={{harvid|Lady Bird Johnson Wildflower Center}} | title=Asplenium platyneuron | work=Native Plant Database | publisher=[[Lady Bird Johnson Wildflower Center]] | url=http://www.wildflower.org/plants/result.php?id_plant=ASPL | access-date=September 22, 2013}}
*{{cite journal | title=As to ''Asplenium ebeneum'' var. ''hortonae'' | last=Leeds | first=Arthur N. | year=1937 | journal=American Fern Journal | volume=27 | issue=1 | pages=30–31 | url=https://www.biodiversitylibrary.org/page/32262481 | doi=10.2307/1544303 |jstor=1544303}}
*{{cite journal | title=Notes on North American ferns | year=1981 | last=Lellinger | first=David B. | author-link=David B. Lellinger | journal=American Fern Journal | volume=71 | issue=3 | pages=90–94 | url=https://www.biodiversitylibrary.org/page/32261847 | doi=10.2307/1546734 |jstor=1546734}}
*{{cite book | first=David B. | last=Lellinger | title=A Field Manual of the Ferns & Fern-Allies of the United States & Canada | url=https://archive.org/details/fieldmanualoffer00lell | url-access=registration | publisher=Smithsonian Institution Press | location=Washington, DC | year=1985 | isbn=0874746035}}
*{{cite book | title=Species Plantarum | volume=II | last=Linnaeus | first=C. | author-link=Carl Linnaeus | year=1753 |lang=la | publisher=Laurentii Salvii | location=Stockholm |url=https://www.biodiversitylibrary.org/page/359090}}
*{{cite book | ref={{harvid|Loddiges1817}} | title=The botanical cabinet | volume=I | author=Conrad Loddiges and Sons | others=George Cooke (illustrator) | author-link=Loddiges | publisher=C. Loddiges & Sons | location=Hackney | year=1817 | url= http://botanicus.org/page/1528696}}
*{{cite book | title=Our native ferns | volume=II | last=Lowe | first=Edward Joseph | author-link=Edward Joseph Lowe | year=1869 | publisher=Groombridge and Sons | location=London | url=https://books.google.com/books?id=X4LPAAAAMAAJ&pg=PA169}}
*{{cite journal | title=Evaluation of fern and moss protein‐based defenses against phytophagous insects | last1=Markham | first1=Kevin | last2=Chalk | first2=Tanya | last3=Stewart | first3=C. Neal Jr. | year=2006 | journal=International Journal of Plant Sciences | volume=167 | issue=1 | pages=111–117 | url=http://plantsciences.utk.edu/pdf/markhamIJPS2006.pdf | doi=10.1086/497651| s2cid=3120202 }}
*{{cite journal | title=Proliferous ebony spleenwort | last=Marshall | first=M. A. | year=1923 | journal=American Fern Journal | volume=13 | issue=1 | pages=7–13 | url=https://www.biodiversitylibrary.org/page/30823776 | doi=10.2307/1543840 |jstor=1543840}}
*{{cite journal | last=Maxon | first=William R. | author-link=William R. Maxon | title=Notes on American ferns—XXII | journal=American Fern Journal | volume=28 | issue=4 | pages=140–144 | year=1938 | url=https://www.biodiversitylibrary.org/page/32262775 | doi=10.2307/1545080 |jstor=1545080}}
*{{cite book | first=André | last=Michaux | author-link=André Michaux | title=Flora boreali-americana |lang=la | volume=2 | publisher=Charles Crapelet | location=Paris | year=1803 | url=http://botanicus.org/page/410943}}
*{{cite journal | title=Suffolk Co.-Wading River | last=Miller | first=E. S. | year=1873 | journal=Bulletin of the Torrey Botanical Club | volume=4 | issue=9 | pages=41–42 | jstor=2476976}}
*{{cite web | ref={{harvid|Missouri Botanical Garden}} | title=Asplenium platyneuron | work=Plant Finder | publisher=[[Missouri Botanical Garden]] | url=http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/plant-finder/plant-details/kc/j460/asplenium-platyneuron.aspx | access-date=September 14, 2013}}
*{{cite journal | last=Momose | first=Sizuo | title=The prothallia of Aspleniaceae (5) | year=1960 | journal=Journal of Japanese Botany | volume=35 | page=324}}
*{{cite NatureServe |id=2.155256 |title=''Asplenium platyneuron'' |date=November 1, 2024 |access-date=November 16, 2024}}{{sfn whitelist|CITEREFNatureServe2024}}
*{{cite journal | title=A study of spore characteristics of the ferns of Indiana | last=Oliver | first=Jeanette C. | year=1968 | journal=[[American Fern Journal]] | volume=58 | issue=1 | pages=5–12 | url=http://biodiversitylibrary.org/page/32263082 | doi=10.2307/1546271| jstor=1546271 }}
*{{cite journal | title=New stations of rare plants-remarkable varieties and observations | last=Peck | first=C. H. | author-link=Charles Horton Peck | year=1869 | journal=Annual Report of the Regents of the University of the State of New York on the Condition of the State Cabinet of Natural History | volume=22 | pages=102–105 | url=https://www.biodiversitylibrary.org/page/35472572}}
*{{cite journal | title=Notes on xerophytic ferns | last=Pickett | first=F. L. | year=1931 | journal=American Fern Journal | volume=21 | issue=2 | pages=49–57 | url=https://www.biodiversitylibrary.org/page/32224049 | doi=10.2307/1543887 |jstor=1543887}}
*{{cite journal | title=Vascular plants of the Northeastern States | last=Robinson | first=B. L. | author-link=Benjamin Lincoln Robinson | year=1908 | journal=Rhodora | volume=10 | issue=110 | pages=29–34 | url=https://www.biodiversitylibrary.org/page/563434 |jstor=23294017}}
*{{cite journal |  volume = 98| issue =12 | year=1966 |pages= 1252–1259 | title=Review of the Fern Aphids in North America With Descriptions of a New Species and a New Genus | first=A. G. | last=Robinson | journal=The Canadian Entomologist | doi=10.4039/Ent981252-12| s2cid =83990776 }}
*{{cite journal | title=Ferns of Duval County, Florida | last=Satchwell | first=Mary W. | year=1916 | journal=American Fern Journal | volume=6 | issue=1 | pages=39–42 | url=https://www.biodiversitylibrary.org/page/30822070 | doi=10.2307/1544707 |jstor=1544707}}
*{{cite book | last=Sim | first=Thomas R. | author-link=Thomas Robertson Sim | title=The Ferns of South Africa | year=1915 | edition=2nd | publisher=Cambridge University Press | location=Cambridge, England | url=https://archive.org/details/fernsofsouthafri00simt| page=[https://archive.org/details/fernsofsouthafri00simt/page/140 140] }}
*{{cite journal | last1=Smith | first1=Dale M. | last2=Bryant | first2=Truman R. | last3=Tate | first3=Donald E. | title=New evidence on the hybrid nature of ''Asplenium kentuckiense'' | journal=[[Brittonia]] | volume=13 | issue=3 | pages=289–292 | year=1961 | doi=10.2307/2805345 |jstor=2805345| s2cid=29551918 }}
*{{cite journal | last1=Smith | first1=Dale M. | last2=Levin | first2=Donald A. | title=A chromatographic study of reticulate evolution in the Appalachian ''Asplenium'' complex | journal=[[American Journal of Botany]] | volume=50 | issue=9 | pages=952–958 | year=1963 | doi=10.2307/2439783 |jstor=2439783}}
*{{cite journal | title=Reports on the flora of Massachusetts-I | last=Smith | first=Lyman B. | author-link=Lyman Bradford Smith | year=1928 | journal=Rhodora | volume=30 | issue=349 | pages=12–19 | url=https://www.biodiversitylibrary.org/page/599977 |jstor=23298120}}
*{{cite book | title=Field guide to the ferns and other pteridophytes of Georgia | last1=Snyder | first1=Lloyd H. Jr. | last2=Bruce | first2=James G. | year=1986| publisher=University of Georgia Press | location=Athens, Georgia | isbn=0-8203-2385-3}}
*{{cite journal | last=Swartz | first=Olof | author-link=Olof Swartz | title=Genera et species filicum |lang=la | journal=Journal für die Botanik (Schrader) | year=1801 | volume=2 | publisher=Heinrich Dieterich | location=Göttingen | url=https://archive.org/stream/journalfrdiebot00schrgoog}}
*{{cite journal | last=Tanger | first=Louise F. A. | title=Ferns and fern allies of Lancaster County, Pennsylvania, 1931 and 1932 | journal=American Fern Journal | year=1933 | volume=23 | issue=1 | pages=13–18 | url=https://www.biodiversitylibrary.org/page/32224356 | doi=10.2307/1544780 |jstor=1544780}}
*{{cite journal | title=Variation in North American ''Asplenium platyneuron'' | last1=Taylor | first1=W. Carl | last2=Mohlenbrock | first2=Robert H. | last3=Burton | first3=Fredda J. | year=1976 | journal=American Fern Journal | volume=66 | issue=2 | pages=63–68 | url=https://www.biodiversitylibrary.org/page/31876390 | doi=10.2307/1546521 |jstor=1546521}}
*{{cite journal | last=Tetrick | first=R. M. II | title=A new form of the brownstem spleenwort | journal=American Fern Journal | year=1949 | volume=39 | issue=3 | pages=92–93 | url=https://www.biodiversitylibrary.org/page/32406636 | doi=10.2307/1545605 |jstor=1545605}}
*{{cite web | ref = {{harvid|Tropicos|2013}} | date = November 2013 | publisher = Tropicos | title = ''Asplenium trichomanoides'' Kunze homonyms | url = http://www.tropicos.org/Name/50210970?tab=homonyms |location=[[Saint Louis, Missouri]] |access-date=22 October 2013}}
*{{cite journal | last=Wagner | first=Warren H. Jr. | author-link=Warren H. Wagner | title=Reticulate Evolution in the Appalachian Aspleniums | journal=[[Evolution (journal)|Evolution]] | volume=8 | year=1954 | issue=2 | pages=103–118 | doi=10.2307/2405636| jstor=2405636 | hdl=2027.42/137493 | url=https://deepblue.lib.umich.edu/bitstream/2027.42/137493/1/evo00117.pdf | hdl-access=free }}
*{{cite journal | last=Wagner | first=Warren H. Jr. | title=''Asplenium ebenoides'' × ''platyneuron'', a new triploid hybrid produced under artificial conditions | journal=American Fern Journal | volume=46 | issue=2 | pages=75–82 | year=1956 | url=https://www.biodiversitylibrary.org/page/31990390 | doi=10.2307/1545364 |jstor=1545364}}
*{{cite journal | title=Natural history of the ebony spleenwort, ''Asplenium platyneuron'' (Aspleniaceae) in the Great Lakes area | year=1981 | last1=Wagner | first1=Warren H. Jr. | last2=Johnson | first2=David M. | journal=[[Canadian Field-Naturalist]] | volume=95 | pages=156–166 | url=https://www.biodiversitylibrary.org/page/28061853}}
*{{cite encyclopedia | year=1993 | title=''Asplenium platyneuron'' | editor=Flora of North America Editorial Committee | last1=Wagner | first1=Warren H. Jr. | last2=Moran | first2=Robbin C. | last3=Werth | first3=Charles R. | authorlink3=Charles R. Werth |encyclopedia=Flora of North America North of Mexico |volume=2: Pteridophytes and Gymnosperms |publisher=Oxford University Press |location=New York and Oxford |url=http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=233500195 |access-date=2012-11-11}}
*{{cite journal | last1=Wagner | first1=Warren H. Jr. | last2=Wagner | first2=Florence S. |authorlink2=Florence Signaigo Wagner | title=Another nothospecies in the Appalachian ''Asplenium'' complex | journal=American Fern Journal | volume=80 | issue=2 | pages=44–49 | year=1990 | url=https://www.biodiversitylibrary.org/page/32152712 | doi=10.2307/1547317 |jstor=1547317}}
*{{cite journal | last1=Walter | first1=Kerry S. | last2=Wagner | first2=Warren H. Jr. | last3=Wagner | first3=Florence S. | title=Ecological, biosystematic, and nomenclatural notes on Scott's spleenwort, ''× Asplenosorus ebenoides'' | journal=American Fern Journal | volume=72 | issue=3 | year=1982 | pages=65–75 | url=https://www.biodiversitylibrary.org/page/31805041 | doi=10.2307/1546598 |jstor=1546598}}
*{{cite journal | last=Waters | first=C. E. | title=Asplenium ebeneum proliferum | year=1903 | journal=Rhodora | volume=5 | issue=59 | pages=272–273 | url=https://www.biodiversitylibrary.org/page/562245 |jstor=23293834}}
*{{cite journal | last=Waters | first=C. E. | title=Asplenium ebeneum proliferum | year=1904 | journal=Rhodora | volume=6 | issue=70 | pages=210–211 | url=https://www.biodiversitylibrary.org/page/562503 |jstor=23293520}}
*{{cite book | last=Weakley | first=Alan | year=2015 | title=Flora of the Southern and Mid-Atlantic States | edition=Working Draft, 21 May 2015 | url=http://www.herbarium.unc.edu/flora.htm | publisher=University of North Carolina}}
*{{cite journal | last=Weatherby | first=C. A. | author-link=Charles Alfred Weatherby | title=The earliest record of proliferous ebony spleenwort | journal=American Fern Journal | year=1924 | volume=14 | issue=3 | pages=95–96 | url=https://www.biodiversitylibrary.org/page/30824030 | doi=10.2307/1544260 |jstor=1544260}}
*{{cite journal | last1=Werth | first1=Charles R. | authorlink1=Charles R. Werth | last2=Guttman | first2=Sheldon I. | last3=Eshbaugh | first3=W. Hardy | authorlink3=W. Hardy Eshbaugh | title=Electrophoretic evidence of reticulate evolution in the Appalachian ''Asplenium'' complex | journal=[[Systematic Botany]] | volume=10 | issue=2 | pages=184–192 | year=1985 | doi=10.2307/2418344 |jstor=2418344}}
*{{cite journal | last=Wherry | first=Edgar T. | author-link=Edgar T. Wherry | year=1920 | title=The soil reactions of certain rock ferns—II | journal=American Fern Journal | volume=10 | issue=2 | pages=45–52 | url=https://www.biodiversitylibrary.org/page/30816893 | doi=10.2307/1543831 |jstor=1543831}}
*{{cite journal | last=Wherry | first=Edgar T. | year=1920b | title=Soil acidity—its nature, measurement, and relation to plant distribution | journal=Annual Report of the Board of Regents of the Smithsonian Institution | volume=1920 | pages=247–268 | url=https://www.biodiversitylibrary.org/page/7939339}}
*{{cite journal | last=Wherry | first=Edgar T. | title=The ferns and lycosphens of Pennsylvania | journal=[[Bartonia (journal)|Bartonia]] | volume=21 | year=1940 | pages=11–37 | url=https://www.biodiversitylibrary.org/page/36395305}}
*{{cite book | first=Carl Ludwig | last=Willdenow | author-link=Carl Ludwig Willdenow | title=Linnaei species plantarum |lang=la | volume=5 pt. 1 | publisher=G. C. Nauk | location=Berlin | year=1810 | url=http://botanicus.org/page/547180}}
*{{cite journal |last1=Xu |first1=Ke-Wang |last2=Zhang |first2=Liang |last3=Rothfels |first3=Carl J. |last4=Smith |first4=Alan R. |last5=Viane |first5=Ronald |last6=Lorence |first6=David |last7=Wood |first7=Kenneth R. |last8=Cheng |first8=Cheng-Wei |last9=Knapp |first9=Ralf |last10=Zhou |first10=Lin |last11=Lu |first11=Ngan Thi |last12=Zhou |first12=Xin-Mao |last13=Wei |first13=Hong-Jin |last14=Fan |first14=Qiang |last15=Chen |first15=Su-Fang |last16=Cicuzza |first16=Daniele |last17=Gao |first17=Xin-Fen |last18=Li |first18=Wen-Bo |last19=Zhang |first19=Li-Bing |title=A global plastid phylogeny of the fern genus Asplenium (Aspleniaceae) |year=2020 |journal=Cladistics |volume=36 |issue=1 |pages=22–71 |doi=10.1111/cla.12384|pmid=34618950 |s2cid=201197385 |doi-access=free }}
{{refend}}

==External links==
* [https://www.paenflowered.org/apgii/polypodiales/aspleniaceae/asplenium/asplenium-platyneuron Flora of Pennsylvania]
{{Taxonbar|from=Q4808139}}

[[Category:Asplenium|platyneuron]]
[[Category:Ferns of the United States]]
[[Category:Ferns of Canada]]
[[Category:Plants described in 1753]]
[[Category:Taxa named by Carl Linnaeus]]