Argyrochosma fendleri

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Argyrochosma fendleri
Argyrochosma fendleri habit.jpg
Argyrochosma fendleri growing in a rock crevice
Status TNC G3.svg
Vulnerable  (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. fendleri
Binomial name
Argyrochosma fendleri
Synonyms
  • Cheilanthes cancellataMickel
  • Cincinalis fendleri(Kunze) Fée
  • Gymnogramma fendleri Mett.
  • Hemionitis engywookii(Kunze) Christenh.
  • Notholaena fendleriKunze
  • Pellaea fendleri(Kunze) Prantl

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 (the "false cloak ferns") in 1987, recognizing their distinctness from the "cloak ferns" ( Notholaena sensu stricto ).

Contents

Description

Argyrochosma fendleri is a medium-sized epipetric fern. The rhizome is compact, 2 to 3 millimeters (0.08 to 0.1 in) wide, and may be horizontal or upright. It bears linear to lanceolate scales 7 to 10 millimeters (0.3 to 0.4 in) long, [2] thin in texture [3] and of a uniform orange-brown [2] or chestnut-brown color [3] with entire (toothless) margins. [4]

Numerous fronds arise in dense clumps from the rhizome. [3] From base to tip of leaf, they are 5 to 25 centimeters (2.0 to 9.8 in) long [5] [2] and 5 to 12 centimeters (2.0 to 4.7 in) wide. [4] Of this length, about half is made up by the stipe (the stalk of the leaf, below the blade), which is round, hairless, and chestnut-brown in color. It typically measures from 0.75 to 1.5 millimeters (0.030 to 0.059 in) in diameter [2] and 3 to 16 centimeters (1.2 to 6.3 in) in length. [4]

The leaf blades are deltate (triangular) in shape, highly divided (from four to six successive subdivisions) at the base, [5] [2] sometimes broader than they are long. [3] They curl slightly upwards when dried. [4] The rachis (leaf axis) is round, rather than flattened, hairless, and zig-zags rather than being straight. [2] Each blade bears 4 to 6 pairs of pinnae, whose costae also zig-zag, with subdivisions branching off at the angles. [2] [3] The ultimate segments are ovate to lanceolate [4] or oblong, [6] obtuse at the tip and broadly cuneate (wedge-shaped) at the base, [6] and sometimes have an crenate (round-toothed) margin. [4] The dark color of the axes passes into the segment base, without a distinct joint, [5] [2] and pinnae and subsequent subdivisions are borne on long stalks. [6] The underside of the leaf is coated in pale white farina (powder), and a scattering of glands and farina is sometimes present on the upper surface. [5] [2] [4] The leaf tissue is leathery to somewhat leafy in texture. [5]

The sori lie along the veins, along the final quarter of the length of the veins closest to the edge of the leaf. [5] The veins themselves tend to blend into the leaf tissue. The leaf edges are not modified into false indusia, and may be flat or curled under to cover the sori. [5] [2] Each sporangium bears 64 spores. The plants are diploid, with a chromosome number of 2n = 54. [5] [2]

The zig-zag rachis and axes generally serve to distinguish it from other members of the genus. [5] A. limitanea may have slightly zig-zag axes, but its subdivisions are not as strongly spreading. [7] Furthermore, A. limitanea is apogamous and only contains 32, rather than 64, spores per sporangium. [5]

Taxonomy

The species was first described by Gustav Kunze in 1851 as Notholaena fendleri, based on material collected in New Mexico by Augustus Fendler, for whom it is named. [8] 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 fendleri in 1852, breaking with most other authorities in recognizing and re-circumscribing that genus. [9] 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. [10] He transferred the species there as G. fendleri. [11] Prantl expanded Pellaea to include several genera in which he perceived close affinities, including Cincinalis. Accordingly, he transferred C. fendleri to Pellaea section Cincinalis as P. fendleri in 1882. [12] In 1979, John T. Mickel transferred it to Cheilanthes as Cheilanthes cancellata (the epithet fendleri was preoccupied), as part of an effort to create a more coherent Notholaena . [13]

Argyrochosma fendleri leaf, showing the coating of white farina below and the characteristic zig-zag axes. Argyrochosma fendleri axes and farina.jpg
Argyrochosma fendleri leaf, showing the coating of white farina below and the characteristic zig-zag axes.

By the late 20th century, most authorities favored placement of Notholaena nivea and closely related ferns, including N. fendleri, 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. [14] 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 , [15] and transferred this species to that genus as A. fendleri. [16] In 2018, Maarten J. M. Christenhusz transferred the species to Hemionitis as H. engywookii (the epithet fendleri was preoccupied), as part of a program to consolidate the cheilanthoid ferns into that genus. The epithet refers to the gnome scientist Engywook in the novel The Neverending Story . [17]

Phylogenetic studies have shown that A. fendleri forms an isolated clade, diverging at an early date from the other two clades of farina-bearing Argyrochosma. [18] Its farina is chemically distinct from that of other Argyrochosma, consisting mostly of eriodictyol-7-methyl ether, a compound rare in ferns. [18]

Distribution and habitat

Argyrochosma fendleri is known in the United States from New Mexico, Colorado, and the southeastern corner of Wyoming, [19] and in Mexico from Sonora. [7]

It grows on rocky cliffs and slopes, particularly on granitic and igneous rocks, the only member of the genus to prefer this substrate. It is found at an altitude from 1,700 to 3,000 meters (5,600 to 9,800 ft). [5]

Conservation

Under the NatureServe conservation status system, A. dealbata is ranked as vulnerable (G3), but it is considered critically imperiled in Wyoming and vulnerable in Colorado. [1]

Cultivation

The horticulturist George Schneider, considered it suitable for conservation, noting that it "thrives well under cool treatment", [20] perhaps in contrast to tropical ferns.

Notes and references

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.

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

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 in 1987, recognizing their distinctness from the "cloak ferns".

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".

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 8 9 10 11 Mickel & Smith 2004, p. 65.
  3. 1 2 3 4 5 Tryon & Weatherby 1956, p. 89.
  4. 1 2 3 4 5 6 7 Lellinger 1985, p. 159.
  5. 1 2 3 4 5 6 7 8 9 10 11 Windham 1993.
  6. 1 2 3 Tryon & Weatherby 1956, p. 90.
  7. 1 2 Mickel & Smith 2004, p. 66.
  8. ↑ Kunze 1851, p. 87.
  9. ↑ Fée 1852.
  10. ↑ Mettenius 1859, pp. 49–51.
  11. ↑ Mettenius 1859, p. 51.
  12. ↑ Prantl 1882, p. 417.
  13. ↑ Mickel 1979, p. 433.
  14. ↑ Windham 1987, p. 37.
  15. ↑ Windham 1987, p. 38.
  16. ↑ Windham 1987, p. 40.
  17. ↑ Christenhusz, Fay & Byng 2018, p. 13.
  18. 1 2 Sigel et al. 2011, pp. 561–562.
  19. ↑ Kartesz 2014.
  20. ↑ Schneider 1892, p. 608.

Works cited

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