Argyrochosma dealbata

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Argyrochosma dealbata
Argyrochosma dealbata habit.jpg
Argyrochosma dealbata growing in a rock crevice.
Status TNC G4.svg
Apparently Secure  (NatureServe) [1]
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Division: Polypodiophyta
Class: Polypodiopsida
Order: Polypodiales
Family: Pteridaceae
Genus: Argyrochosma
Species:
A. dealbata
Binomial name
Argyrochosma dealbata
Synonyms
  • Cheilanthes dealbataPursh
  • Cincinalis dealbata(Pursh) Fée
  • Gymnogramma dealbata(Pursh) Mett., nom. illeg. hom.
  • Hemionitis artax Christenh.
  • Notholaena dealbata(Pursh) Kunze
  • Notholaena nivea var. dealbata(Pursh) Davenp.
  • Notholaena pulchellaKunze
  • Pellaea dealbata(Pursh) Prantl

Argyrochosma dealbata, the powdery false cloak fern, is a small fern endemic to the central and southern United States. It grows on calcareous rocks, such as limestone. Its leaves are highly divided, with leaf segments joined by shiny, chestnut-brown axes, and their undersides are coated with white powder, giving the fern its name. First described as a species in 1814, it was transferred to the new genus Argyrochosma (the "false cloak ferns") in 1987, recognizing their distinctness from the "cloak ferns" ( Notholaena sensu stricto ).

Contents

Description

Argyrochosma dealbata leaf blade, showing a few glands dotted on the upper surface. Argyrochosma dealbata frond adaxial.jpg
Argyrochosma dealbata leaf blade, showing a few glands dotted on the upper surface.

The rhizome is compact, more or less upright, and usually unbranching, [2] and bears brown, [3] pale brown [4] or yellowish-brown [5] scales that are uniform in color. [4] [5] These are about 3 millimeters (0.1 in) long, thin and delicate, [4] narrowly lanceate [5] or linear [4] and entire (toothless) at the edges. [4] [5]

The fronds of A. dealbata spring from the rhizome in clusters [2] [4] and are 3 to 15 centimeters (1 to 6 in) long. [3] The stipe (the stalk of the leaf, below the blade) is a shiny [2] pale to medium brown, [5] chestnut brown, [3] or reddish-brown in color, [2] measuring 2 to 7 centimeters (0.8 to 3 in) long [5] and 0.50 to 0.75 millimeters (0.020 to 0.030 in) in diameter. [3] It is rounded (rather than flattened or grooved) and lacks extensive hairs or scales; [4] a few rhizome scales may be present at its base. [5] The shiny brown color of the stipe continues into the rachis and the axis of the leaf segments, and blends with the leaf tissue at the base of each segment, without an abrupt end point. [2] [3] The rachis (leaf axis) is rounded or slightly flattened on the upper surface. The costae (pinna axes) are more or less straight. [3] The axes tend to curl upwards when dry. [6]

The leaf blades are deltate (triangular) [3] or lanceolate, [5] broadest at the base, and are most highly divided there, ranging from tripinnate (cut into pinnae, pinnules, and pinnulets) to pentapinnate (five times divided). [3] They are 2 to 6 centimeters (0.8 to 2 in) long and 1.5 to 6 centimeters (0.6 to 2 in) wide, [5] obtuse (blunt) to acute (pointed) at the base and acute at the tip. [7] 3 to 5 pairs of pinnae are present. They are roughly deltate in shape and attached to the rachis by a long stalk. [4] The final divisions of the blade are oblong to ovate, [4] [6] and the dark color of the axes passes into their base, without a distinct joint. [4] The blade tissue is bluish green [2] and somewhat leafy in texture (rather than densely leathery); veins are often visible on the upper surface of the leaf. [3] and a whitish (or rarely, yellowish) [4] farina (powder) covers the underside, while the upper surface is free of hairs, powder, etc., although it may bear a few glands. [3] [6] The edges of leaf segments curl back under and partially protect the sori, which are borne along veins close to the edge. The sporangia contain 64 spores, released in summer and fall. Plants are sexual diploids, with a chromosome number of 2n = 54. [3]

Taxonomy

Underside of a leaf, showing the coating of white farina that gives the species its name. Argyrochosma dealbata frond abaxial.jpg
Underside of a leaf, showing the coating of white farina that gives the species its name.

Like many cheilanthoid ferns, this species has been placed in many genera at different times. It was first described by Pursh in 1814 as Cheilanthes dealbata, based on material collected on the banks of the Missouri River. The epithet dealbata, meaning "covered in white powder", [8] refers to the coating of farina on the underside of the leaves. [9] Gustav Kunze independently described the species as Notholaena pulchella in 1843. His specimen was collected for the Berlin Botanical Garden from rocks in Missouri. Initially misidentified as Notholaena nivea , he noted that the Missouri material was smaller and more highly divided, and commented on the white powder on the underside of the leaves, lacking in Pursh's description. [10] The epithet pulchella means "small and beautiful". [11] He subsequently recognized it as synonymous with C. dealbata and transferred the older name to Notholaena as N. dealbata in 1848, noting that he "would not have looked for it under Cheilanthes". [12] [lower-alpha 1]

Delineating natural genera in the cheilanthoids has proven to be extremely difficult, and other placements of the species were subsequently put forward. Fée transferred it to Cincinalis as Cincinalis dealbata in 1852, breaking with most other authorities in recognizing and re-circumscribing that genus. [13] In 1859, Mettenius rejected Fée's attempt to delineate Cincinalis as a separate genus, but recognized the genus Gymnogramma for species where sporangia were borne along the nerves and not densely clustered at the end of the nerves. [14] He transferred the species there as G. dealbata, [15] but this name had already been used by Presl for a different species in 1825, rendering it illegitimate. Prantl expanded Pellaea to include several genera in which he perceived close affinities, including Cincinalis. Accordingly, he transferred C. dealbata to Pellaea section Cincinalis as P. dealbata in 1882. [16] George Edward Davenport lumped it as a variety of N. nivea, N. nivea var. dealbata, in 1883. [17]

By the late 20th century, most authorities favored placement of Notholaena nivea and closely related ferns, including N. dealbata, either in Notholaena or Pellaea. Both Edwin Copeland and C. A. Weatherby suggested in the 1940s that this group of ferns might represent a distinct genus of its own. [18] This was finally addressed in 1987 by Michael D. Windham, who was carrying out phylogenetic studies of these genera. He elevated Notholaena sect. Argyrochosma to become the genus Argyrochosma , [19] and transferred this species to that genus as A. dealbata. [20] In 2018, Maarten J. M. Christenhusz transferred the species to Hemionitis as H. artax (the epithet dealbata was preoccupied), as part of a program to consolidate the cheilanthoid ferns into that genus. The epithet refers to the horse of Atreyu in the novel The Neverending Story . [21]

Phylogenetic studies have shown that A. dealbata is a sister species to A. limitanea , of the southwestern United States and northern Mexico; these two species form a clade sister to another clade of several South American species. [22]

Species of Argyrochosma are commonly referred to as "false cloak ferns"; the name apparently refers to their resemblance to Notholaena proper, known as "cloak ferns" for the reflexed leaf margins, which cloak the sporangia.

Distribution and habitat

Argyrochosma dealbata is endemic to the United States. It is found from the western edge of Illinois south and west through Arkansas and Missouri to southeastern Nebraska and thence south through Kansas and Oklahoma to Texas, with a disjunct station in south-central Kentucky. [23]

It grows in the crevices of cliffs or ledges of calcareous rock. [3] [6]

Conservation

Under the NatureServe conservation status system, A. dealbata is ranked as apparently secure (G4), but it is considered imperiled in Arkansas and Oklahoma, and the single occurrences in Nebraska and Kentucky are considered extirpated and historical, respectively. [1]

Cultivation

Kunze suggested the species was suitable for cultivation, noting that it was grown in Berlin in a well-lit part of the greenhouses. [24] George Schneider suggested it required "cool treatment", perhaps in contrast to the desert-dwelling members of the genus. [25] It has been described as preferring medium light, and relatively dry, well-drained soil mixed with sand, perhaps of high pH. [2]

Notes and references

Notes

  1. ↑ Cheilanthes and Notholaena were formerly distinguished by the morphology of their false indusia: broken into multiple segments in the first genus and largely continuous in the second. This has since proven to be an artificial distinction, of little value in identifying the relationships between cheilanthoids.

Related Research Articles

<i>Argyrochosma</i> Genus of ferns in the family Pteridaceae

Argyrochosma is a genus of ferns known commonly as false cloak ferns. The genus is included in the Cheilanthoideae subfamily of the Pteridaceae. Species now in this genus were previously treated as members of related genera Notholaena or Pellaea but were segregated into their own genus in 1987. These ferns, of which there are about 20 species, are mostly native to the Americas, from North to South and including the Caribbean, while one species, A. connectens, is known from Sichuan, China. They are commonly found growing in cracks between rocks. Their leaves are generally shorter than 40 centimeters and have rounded bluish or grayish green segments. Often the lower surface of the segments is coated in a white dust, and the sporangia contain brown spores.

<i>Argyrochosma jonesii</i> Species of fern in the family Pteridaceae

Argyrochosma jonesii, known as Jones' false cloak fern, is a species of fern native to the southwestern United States and Sonora, Mexico. It grows on calcareous rocks, and has small, finely-divided leaves with a leathery texture and dark axes connecting the leaf segments. Unlike many members of Argyrochosma, it does not secrete white powder on the underside of its leaves. First described as a species in 1917, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

<i>Argyrochosma nivea</i> Species of fern in the family Pteridaceae

Argyrochosma nivea is an Andean fern species in the genus Argyrochosma.

<i>Myriopteris alabamensis</i> Species of fern

Myriopteris alabamensis, the Alabama lip fern, is a moderately-sized fern of the United States and Mexico, a member of the family Pteridaceae. Unlike many members of its genus, its leaves have a few hairs on upper and lower surfaces, or lack them entirely. One of the cheilanthoid ferns, it was usually classified in the genus Cheilanthes as Cheilanthes alabamensis until 2013, when the genus Myriopteris was again recognized as separate from Cheilanthes. It typically grows in shade on limestone outcrops.

Myriopteris allosuroides is a moderately-sized fern of Mexico, a member of the family Pteridaceae. Unlike many members of its genus, its rachides are grooved on the upper surface and largely free of hairs or scales. One of the cheilanthoid ferns, it was usually classified in the genera Cheilanthes or Pellaea until 2013, when the genus Myriopteris was again recognized as separate from Cheilanthes. It typically grows on dry, rocky slopes over acidic, particularly basaltic, rock.

Argyrochosma connectens is a small cheilanthoid fern endemic to Sichuan, China. It is the only member of its genus known from Asia. Relatively rare, it is found growing in the crevices of limestone rocks in hot, dry valleys. The species was long classified in the genus Pellaea, but after a phylogenetic study in 2015 was transferred to Argyrochosma.

Argyrochosma delicatula is a fern known from northeastern Mexico. It grows in rocky habitats, either in sun or in shade, and is distinguished from similar species by the presence of pale yellow powder on the underside of its leaves. First described as a species in 1939, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

<i>Argyrochosma peninsularis</i> Species of fern in the family Pteridaceae

Argyrochosma peninsularis is a fern endemic to Baja California Sur. It grows in dry, rocky places. First described as a species in 1939, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns". A dusting of powdery material and the presence of occasional scales on the central axis of its leaves help distinguish it from related species.

Argyrochosma pallens is a fern endemic to Mexico. It has narrow, divided leaves with brown axes; the leaves are dusted with white powder above and coated in it below. First described as a species in 1956, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

Argyrochosma chilensis is a fern endemic to the Juan Fernández Islands off the coast of Chile. It has leathery, thrice-divided leaves with dark brown axes; the leaves are coated with white powder below. First described as a species in 1853, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

Argyrochosma stuebeliana is a fern endemic to Peru. Its highly divided, leathery leaves are coated with white powder on their under surface. Originally described as a variety of Argyrochosma dealbata in 1909, based on a single leaf collected by Alphons Stübel, whom its name honors, it was recognized as a distinct species in 1961, distinguished from similar members of the genus largely by its round leaf segments. It was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

<i>Myriopteris aurea</i> Species of fern

Myriopteris aurea, the golden lip fern or Bonaire lip fern, is a moderately-sized fern native to the Americas, a member of the family Pteridaceae. Unlike many members of its genus, its leaf is only modestly dissected into lobed leaflets (pinnae), which are hairy both above and below. One of the cheilanthoid ferns, until 2013 it was classified in the genus Cheilanthes as Cheilanthes bonariensis, when the genus Myriopteris was again recognized as separate from Cheilanthes. It typically grows on dry, rocky slopes, and ranges from Mexico, where it is common and widespread, and the southwestern United States south and east through Central and South America as far as Chile and Argentina.

Argyrochosma lumholtzii is a rare fern in the family Pteridaceae known from Sonora, Mexico. It is quite similar to Jones' false cloak fern, but has black leaf axes and a less highly divided leaf. First described as a species in 1939, honoring the explorer Carl Sofus Lumholtz, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

<i>Argyrochosma fendleri</i> Species of fern in the family Pteridaceae

Argyrochosma fendleri, Fendler's false cloak fern, is a fern known from the western United States and northwestern Mexico. It grows in rocky habitats, and is distinguished from other members of the genus by its zig-zag leaf axes. Like many species in the genus, it bears white powder on the underside of its leaves. First described as a species in 1851, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

Argyrochosma incana, the hairy false cloak fern, is a fern known from the southwestern United States through Mexico to Guatemala, and from a disjunct population in the Dominican Republic. It grows on rocky slopes and steep banks, often in forests. Like many of the false cloak ferns, it bears white powder on the underside of its leaves. First described as a species in 1825, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

Argyrochosma palmeri is a fern endemic to Mexico. It has narrow, divided leaves with black axes; the leaves are coated in white powder below, and sparsely dusted or free of it above. First described as a species in 1887, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

Argyrochosma pilifera is a fern endemic to Mexico. It has lance-shaped, divided leaves with dark purple axes; the undersides of the leaves are coated in white powder. First described as a species in 1956, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

<i>Argyrochosma formosa</i> Species of fern in the family Pteridaceae

Argyrochosma formosa is a fern known from eastern and central Mexico and Guatemala. It grows on rocky slopes, particularly on limestone. Unlike many members of the genus, it lacks white powder on the underside of its leaves. First described as a species in 1842, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

<i>Argyrochosma limitanea</i> Species of fern in the family Pteridaceae

Argyrochosma limitanea, the southwestern false cloak fern, is a species of fern native to the southwestern United States and Sonora, Mexico. It grows on calcareous rocks, and has small, finely-divided leaves with a leathery texture, dark axes connecting the leaf segments, and a heavy coating of white powder on the undersurface. It reproduces apogamously; two subspecies are recognized, which may have originated independently through the hybridization of other taxa not yet discovered. First described as a species in 1919, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

<i>Argyrochosma microphylla</i> Species of fern in the family Pteridaceae

Argyrochosma microphylla, the small-leaf false cloak fern, is a species of fern native to New Mexico, Texas and northern Mexico. It grows on limestone rocks and cliffs, and has finely-divided leaves with small leaf segments, often folded in half when dry, which lack the white powder present on the leaf underside of many related species. First described as a species in 1869, it was transferred to the new genus Argyrochosma in 1987, recognizing their distinctness from the "cloak ferns".

References

  1. 1 2 NatureServe 2020.
  2. 1 2 3 4 5 6 7 Hoshizaki & Moran 2001, p. 189.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 Windham 1993.
  4. 1 2 3 4 5 6 7 8 9 10 11 Tryon & Weatherby 1956, p. 89.
  5. 1 2 3 4 5 6 7 8 9 Lellinger 1985, p. 160.
  6. 1 2 3 4 Lellinger 1985, p. 161.
  7. ↑ Lellinger 1985, pp. 160–161.
  8. ↑ Short & George 2013, p. 153.
  9. ↑ Pursh 1814, p. 671.
  10. ↑ Kunze 1843, pp. 633–634.
  11. ↑ Short & George 2013, p. 236.
  12. ↑ Kunze 1848, pp. 82–83.
  13. ↑ Fée 1852.
  14. ↑ Mettenius 1859, pp. 49–51.
  15. ↑ Mettenius 1859, p. 50.
  16. ↑ Prantl 1882, p. 417.
  17. ↑ Davenport 1883, p. 44.
  18. ↑ Windham 1987, p. 37.
  19. ↑ Windham 1987, p. 38.
  20. ↑ Windham 1987, p. 40.
  21. ↑ Christenhusz, Fay & Byng 2018, p. 10.
  22. ↑ Sigel et al. 2011, pp. 558, 561.
  23. ↑ Kartesz 2014.
  24. ↑ Kunze 1843, p. 635.
  25. ↑ Schneider 1892, p. 606.

Works cited

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