Argyrochosma pallens

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Argyrochosma pallens
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Division: Polypodiophyta
Class: Polypodiopsida
Order: Polypodiales
Family: Pteridaceae
Genus: Argyrochosma
Species:
A. pallens
Binomial name
Argyrochosma pallens
Synonyms
  • Cheilanthes pallens(Weath. ex R. M. Tryon) Mickel & Beitel, nom. illeg. hom.
  • Hemionitis pallens(Weath. ex R. M. Tryon) Christenh.
  • Notholaena pallensWeath. ex R. M. Tryon

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

Contents

Description

Argyrochosma pallens is a medium-sized epipetric fern. The rhizome may be upright or decumbent (horizontal, curving upward at the tip). It bears linear to lanceolate scales 2 to 5 millimeters (0.08 to 0.2 in) long that terminate in a fine hair, of a uniform reddish-brown color, with entire (toothless) margins. [1]

The fronds arise in clumps from the rhizome. From base to tip of leaf, they are up to 20 centimeters (7.9 in) long. Of this length, from 20% to 33% is made up by the stipe (the stalk of the leaf, below the blade). Both stipe and rachis (leaf axis) are round and chestnut-brown, bearing farina (powder) and a scattering of narrow linear or slightly lance-shaped scales 1 to 2 millimeters (0.04 to 0.08 in) of the same color. [1] [2]

The leaf blades are 1 to 2 centimeters (0.4 to 0.8 in) wide and narrowly oblong. They are bipinnate-pinnatifid to tripinnate (cut into pinnae and pinnules that are either deeply lobed or cut into pinnulets). The leaf segments are oblong to broadly deltate-ovate, and are obtuse (blunt) at the tip. The brown color of the axes does pass somewhat into the leaf tissue, but not strikingly so. [1] The upper side of the leaf is covered with a scattering of white farina, which thickly covers the under side. [1] [2]

The sori lie along the veins, forming a band near the perimeter of the leaf segment only 0.5 to 1 millimeter (0.02 to 0.04 in) wide. The leaf edges are slightly curved under, but not otherwise modified into false indusia. The plants are diploid, with a chromosome number of 2n = 54. [1]

It is similar to Argyrochosma incana and can be somewhat difficult to distinguish from that species. However, its leaf blades are widest above the base (rather than at the base), and its rachides and stipes are shiny chestnut-brown and decorated with farina and scales (rather than black and free of ornament). [3] It may also be mistaken for A. palmeri, but that species has darker leaf axes, without scales, and less farina on the upper surface. [4]

Taxonomy

Notholaena pallens was first described by Rolla M. Tryon Jr. in 1956. The name was originally invented by Charles Alfred Weatherby while working on a revision of Notholaena , but he died before completing it and it was left to Tryon to finish and publish. The description is based on material collected by Cyrus Pringle in Durango. It had theretofore been identified as N. palmeri; however, the type specimen of that species was observed to have a black, rather than a chestnut-brown, rachis, lacking glands and scales, differentiating it from the material that had been assigned that name and necessitating the description of a new species for the latter. [5] The epithet pallens means "pale"; [6] no explanation for it was given. While Tryon considered it impossible to reasonably subdivide Notholaena into sections based on the data available at the time, [7] both Edwin Copeland and Weatherby himself had suggested in the 1940s that a group of ferns related to N. nivea might represent a distinct genus of its own. [8] 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 , [9] and transferred this species to that genus as A. pallens. [10] In the following year, it was transferred by John Mickel and Joseph Beitel into Cheilanthes as C. pallens, but this name had already been published in 1827, rendering it illegitimate. [1] In 2018, Maarten J. M. Christenhusz transferred the species to Hemionitis as H. pallens, as part of a program to consolidate the cheilanthoid ferns into that genus. [11]

It lies within a subclade of the genus that also contains A. delicatula, A. incana, A. peninsularis, A. palmeri, and A. pilifera. All members of the clade share pale farina principally composed of terpenoid compounds, unlike the dihydrostilbenoids found in the farina of other members of the genus. [12]

Distribution and habitat

Argyrochosma pallens is endemic to Mexico, occurring from Chihuahua southeast through central Mexico as far as Oaxaca. [3]

It is found on cliffs and ledges, usually limestone ones, particularly within the spiny matorral, at altitudes from 1,500 to 2,920 meters (4,920 to 9,580 ft). [3]

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 cm (16 in) 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 family Pteridaceae.

Myriopteris allosuroides is a moderately-sized fern endemic to 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 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. It was originally described as a variety of Argyrochosma dealbata in 1909, based on a single leaf collected by Alphons Stübel, whom its name honors. In 1961, it was recognized as a distinct species, 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 in family Pteridaceae

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".

Myriopteris cinnamomea is a Central American fern. It is very similar to M. mickelii of southern Mexico and to other species in the "alabamensis clade" of Myriopteris. It is modestly sized, with leaves not more than 30 centimeters (12 in) long. They are divided into pinnae, which in turn are divided into lobed pinnules, and covered with pale brown hairs on the underside.

References

  1. 1 2 3 4 5 6 Mickel & Smith 2004, p. 69.
  2. 1 2 Tryon & Weatherby 1956, p. 14.
  3. 1 2 3 Mickel & Smith 2004, p. 70.
  4. ↑ Mickel & Smith 2004, p. 64–65.
  5. ↑ Tryon & Weatherby 1956, pp. 78–79.
  6. ↑ Short & George 2013, p. 223.
  7. ↑ Tryon & Weatherby 1956, p. 6.
  8. ↑ Windham 1987, p. 37.
  9. ↑ Windham 1987, p. 38.
  10. ↑ Windham 1987, p. 40.
  11. ↑ Christenhusz, Fay & Byng 2018, p. 19.
  12. ↑ Sigel et al. 2011, p. 561.

Works cited

  • Christenhusz, Maarten J. M.; Fay, Michael F.; Byng, James W. (2018). Plant Gateway's the Global Flora: A practical flora to vascular plant species of the world. Vol. 4. ISBN   978-0-9929993-9-1.
  • Mickel, John T.; Smith, Alan R. (2004). The Pteridophytes of Mexico. Memoirs of the New York Botanical Garden. Vol. 88. Bronx, New York: New York Botanical Garden. ISBN   978-0-89327-488-7.
  • Short, Emma; George, Alex (2013). A Primer of Botanical Latin with Vocabulary. Cambridge, England: Cambridge University Press. ISBN   978-1-107-69375-3.
  • Sigel, Erin M.; Windham, Michael D.; Huiet, Layne; Yatskievych, George; Pryer, Kathleen M. (2011). "Species Relationships and Farina Evolution in the Cheilanthoid Fern Genus Argyrochosma (Pteridaceae)". Systematic Botany. 36 (3): 554–564. doi:10.1600/036364411X583547. JSTOR   23028975.
  • Tryon, Rolla M.; Weatherby, Una F. (1956). "A revision of the American species of Notholaena". Contributions from the Gray Herbarium of Harvard University (179): 1–106. doi: 10.5962/p.336378 . JSTOR   41764632.
  • Windham, Michael D. (1987). "Argyrochosma, a new genus of cheilanthoid ferns". American Fern Journal. 77 (2): 37–41. doi:10.2307/1547438. JSTOR   1547438.
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