Argyrochosma formosa

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Argyrochosma formosa
Argyrochosma formosa overall habit.jpg
Argyrochosma formosa, showing black axes and triangular shape of leaf
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Division: Polypodiophyta
Class: Polypodiopsida
Order: Polypodiales
Family: Pteridaceae
Genus: Argyrochosma
Species:
A. formosa
Binomial name
Argyrochosma formosa
Synonyms
  • Allosorus formosusLiebm.
  • Allosorus pulchellus M.Martens & Galeotti, nom. illeg. hom.
  • Cassebeera pulchella Farwell
  • Cheilanthes formosa(Liebm.) Mickel & Beitel
  • Cincinalis pulchella J.Sm.
  • Hemionitis formosa(Liebm.) Christenh.
  • Notholaena formosa(Liebm.) R.M.Tryon
  • Pellaea formosa(Liebm.) Maxon, nom. superfl.
  • Pellaea puchella Fée
  • Platyloma pulchellum T.Moore

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

Contents

Description

Argyrochosma formosa is a medium-sized epipetric fern. The rhizome is compact and horizontal. [1] It bears linear scales 3 to 6 millimeters (0.1 to 0.2 in) [2] or 6 to 9 millimeters (0.2 to 0.4 in) long and 0.3 millimeters (0.01 in) wide, [1] hair-tipped [2] and with entire (toothless) margins. [3] They range from tan to dark orange [1] or rusty in color [2] and feel oily-viscid. [3]

The fronds arise in clumps from the rhizome. They are from about 15 to 40 centimeters (5.9 to 16 in) long, [3] [1] sometimes as short as 10 centimeters (3.9 in), and 2 to 7 centimeters (0.8 to 3 in) broad. [2] Of their length, about 25% to 50% is made up by the stipe (the stalk of the leaf, below the blade), which is shiny or sometimes glaucous and round, hairless, and reddish-brown to dark purple or black in color. [1] [3] The rhizome scales may continue to the base of the stipe. [2] [3]

The leaf blades are tripinnate to quadripinnate (cut into pinnae, pinnules and pinnulets, those sometimes fully cut) and range in shape from ovate to long-deltate (triangular) to ovate-lanceolate. [1] [3] The rachis (leaf axis) is round, rather than flattened. [1] The rachis and the axes of the leaf segments are all dark in color; the color stops abruptly at a joint at the base of the leaf segment. [1] Each blade bears 6 to 9 pairs of pinnae, borne alternately or nearly oppositely on the rachis, [1] with an acute (pointed) tip. [3] The ultimate segments of the blade are orbicular (circular) or inequilaterally cordate (asymmetrically heart-shaped), 3 to 4 millimeters (0.1 to 0.2 in) long, [1] sometimes to 6 millimeters (0.2 in). [2] They are borne on short stalks. [3] The underside of the leaf lacks the farina (powder) that characterizes many members of the genus, [1] although both upper and lower surfaces of the leaf are usually glaucous. [3]

The sori lie along the veins, forming a band 0.5 to 1 millimeter (0.02 to 0.04 in) wide [1] on the outermost quarter of the vein. [3] The leaf edges are curved under, [3] sometimes to the point of touching one another, [2] but otherwise not modified into false indusia. Fertile segments often fold along their long axis, giving them a sagittate (arrowhead-like) shape. Specimens from Oaxaca were found to be apomictic triploids, with a chromosome number of n = 2n = 81. [1]

While it is similar in overall appearance to A. incana , it is easily distinguished from that species by its lack of farina. In Mexico, the only other member of the genus to lack farina is A. microphylla , which has smaller leaf segments, chestnut-brown, rather than black, leaf axes, [1] a grooved rachis and dry rhizome scales. [3]

Taxonomy

The species was first described in 1842 as Allosorus pulchellus by Martin Martens & Henri Guillaume Galeotti, based on material collected by Galeotti in Mexico. [4] The epithet pulchellus means "small and beautiful" [5] and presumably reflects the aesthetic appeal of the species, which they described as "charmante". [4] However, that name had already been used in 1836 for a different species, the former Cheilanthes pulchella , by Carl Borivoj Presl, rendering it nomenclaturally illegitimate. Frederik Liebmann recognized the issue and corrected it by giving Martens & Galeotti's species the replacement name Allosorus formosus in 1849; [6] the epithet formosus means "beautiful". [7]

Delineating natural genera in the cheilanthoids has proven to be extremely difficult, and other placements of the species were subsequently put forward, mostly as replacement names for A. pulchellus in other genera using the same epithet. Fée transferred it to Pellaea as Pellaea pulchella in 1852. [8] In 1857, Thomas Moore, in his Index Filicum, transferred it to Platyloma , a genus he recognized as a segregate from Pellaea, as Platyloma pulchellum. [9] John Smith, in 1866, preferred to recognize a different cheilanthoid segregate, Cincinalis , and placed it there as Cincinalis pulchella. [10] In 1922, William Ralph Maxon created a new combination for Liebmann's name in Pellaea, as Pellaea formosa due to the illegitimacy of Martens & Galeotti's name, [11] although subsequent changes to the practice of nomenclature would make it superfluous. Oliver Atkins Farwell, following a program of reviving what he considered to be senior synonyms, gave Cassebeera priority over Pellaea and transferred the species there as Cassebeera pulchella in 1931. [12]

Maxon and Charles Alfred Weatherby placed Pellaea formosa within a group of ferns closely related to Notholaena nivea, but declined to make a nomenclatural transfer until the classification of the cheilanthoids was better understood. [13] Both Edwin Copeland and 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. formosa. [16] Meanwhile, John Mickel and Joe Beitel had transferred the species to Cheilanthes as C. formosa in their monograph on the ferns of Oaxaca, which was published in 1988; [17] Mickel and Alan R. Smith recognized Argyrochosma in 2004 when preparing a fern flora of Mexico. [1] In 2018, Maarten J. M. Christenhusz transferred the species to Hemionitis as H. formosa, as part of a program to consolidate the cheilanthoid ferns into that genus. [18]

Argyrochosma formosa, showing lack of farina and dark color of axes passing into leaf segments Argyrochosma formosa leaf underside.jpg
Argyrochosma formosa, showing lack of farina and dark color of axes passing into leaf segments

Phylogenetic studies have shown that A. formosa is a sister species to A. microphylla; these two species form a clade sister to another clade containing A. jonesii and A. lumholtzii. [19] All four species lack farina, and their common ancestor is hypothesized to have diverged from the ancestor of the rest of the genus before farina production developed in the latter. [20]

Distribution and habitat

Argyrochosma formosa is distributed from the northernmost provinces of Mexico through eastern and central Mexico to Chiapas and into Guatemala. [1]

In Mexico, it grows on dry rocky slopes and in ravines, often on limestone, as well as in thorny scrub. It has been found growing in mortar at Monte Albán. [1] Most common in similar habitats in Guatemala, it also occurs on hillsides and riverbanks, and in forests and thickets. [2] It is found at an altitude from 1,250 to 2,700 meters (4,100 to 8,860 ft). [1]

Notes and references

Related Research Articles

<i>Notholaena</i> Genus of ferns

Notholaena, cloak fern, is a genus of ferns in the Cheilanthoideae subfamily of the Pteridaceae. Ferns of this genus are mostly epipetric or occurring in coarse, gravelly soils, and are most abundant and diverse in the mountain ranges of warm arid or semiarid regions. They typically have a creeping or erect rhizome and leaves that are pinnatifid to pinnate-pinnatifid with marginal sori protected by a false indusium formed from the reflexed margin of the leaf. Members of Notholaena also have a coating of whitish or yellowish farina on the surfaces of the leaves. The farina is often limited to the abaxial (lower) leaf surface, but may occur on the adaxial (upper) leaf surface as well. Members of the related Pentagramma genus have a similar lower leaf-surface farina.

<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.

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".

<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 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 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Mickel & Smith 2004, p. 66.
  2. 1 2 3 4 5 6 7 8 Stolze 1981, p. 337.
  3. 1 2 3 4 5 6 7 8 9 10 11 12 Tryon & Weatherby 1956, p. 100.
  4. 1 2 Martens & Galeotti 1842, p. 47.
  5. ↑ Short & George 2013, p. 236.
  6. ↑ Liebmann 1849, p. 220.
  7. ↑ Short & George 2013, p. 175.
  8. ↑ Fée 1852.
  9. ↑ Moore 1857, p. lxvi.
  10. ↑ Smith 1866, p. 178.
  11. ↑ Maxon 1922, p. 61.
  12. ↑ Farwell 1931, p. 281.
  13. ↑ Maxon & Weatherby 1939, p. 4.
  14. ↑ Windham 1987, p. 37.
  15. ↑ Windham 1987, p. 38.
  16. ↑ Windham 1987, p. 40.
  17. ↑ Mickel & Beitel 1988, p. 115.
  18. ↑ Christenhusz, Fay & Byng 2018, p. 14.
  19. ↑ Sigel et al. 2011, p. 558.
  20. ↑ Sigel et al. 2011, p. 559.

Works cited

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