Английская Википедия:Argyrochosma jonesii

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Шаблон:Short description Шаблон:Speciesbox

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

Description

The rhizome is short and horizontal, with leaves closely spaced.Шаблон:Sfn It bears linearШаблон:Sfn or linear-subulate,Шаблон:Sfn uniformly colored, brown or reddish-brown scales,Шаблон:Sfn sometimes nearly black in color,Шаблон:Sfn with entire (toothless) marginsШаблон:Sfn and a thin texture.Шаблон:Sfn They are Шаблон:Convert long and Шаблон:Convert wide.Шаблон:Sfn

The leaves range from Шаблон:Convert long,Шаблон:SfnШаблон:Sfn and arise in clumps.Шаблон:SfnШаблон:Sfn The stipe (the stalk of the leaf, below the blade) is chestnut brown or reddish-brown to dark brown, rounded and hairless,Шаблон:SfnШаблон:SfnШаблон:SfnШаблон:Sfn and Шаблон:Convert in diameter.Шаблон:Sfn It is typically Шаблон:Convert long,Шаблон:Sfn making up about one-half to two-thirds of the total length of the leaf.Шаблон:Sfn The leaf blade is ovate to lanceolate, and ranges from bipinnate (cut into pinnae and pinnules) to tripinnate (with pinnules cut into pinnulets) at the base, where it is most divided.Шаблон:SfnШаблон:SfnШаблон:SfnШаблон:Sfn It is not reduced in width at the base.Шаблон:Sfn The blade measures from Шаблон:Convert long and Шаблон:Convert wide.Шаблон:Sfn The base is obtuse (blunt), while the tip is acute (pointed).Шаблон:Sfn The rachis (leaf axis) is rounded or slightly flattened on the upper side, sometimes even shallowly grooved,Шаблон:Sfn and dark in color, as are the axes of the leaf segments. The color continues into the base of the leaf segments, without a distinct joint. The axes are straight, rather than zig-zagging.Шаблон:SfnШаблон:Sfn Each blade has 4 to 6 pairs of pinnae, ovate or deltoid-ovate in shape.Шаблон:Sfn These are in turn divided into 2 to 3 pairsШаблон:Sfn of orbicular (circular)Шаблон:Sfn or deltoid to ovate pinnules, obtuse at the tip and cordate (heart-shaped) or truncate (abruptly terminating) at the baseШаблон:Sfn and borne on a short stalk.Шаблон:Sfn The ones closest to the blade base may be subdivided into another set of segments, while the pinnules closer to the blade tip are lobed or entire.Шаблон:Sfn The leaf tissue is dark blue-greenШаблон:Sfn and of a leathery to fleshy texture,Шаблон:Sfn obscuring the veins from the upper surface, and does not bear hairs or scales on either surface. Unlike many species in the genus, farina (powder) is not present on either surface of the leaf.Шаблон:SfnШаблон:Sfn The leaves do not curl when dry.Шаблон:Sfn

In fertile leaf segments, the sporangia are close to the margin, borne along the further half of the secondary veins branching from the midrib of the segment. Each sporangium contains 64 spores. The leaf segments, at most, are slightly curled under, not concealing the sporangia, and their tissue is not modified into a false indusium.Шаблон:SfnШаблон:Sfn

underside of greenish-gray divided leaflet with brown stalks and empty brown capsules, lacking white powder
Argyrochosma jonesii leaflet, showing slightly curled leaf margins, exposed sporangia, and dark color entering base of leaf segments.

A. jonesii is a sexual diploid, with a chromosome count of 2n = 54.Шаблон:SfnШаблон:Sfn A tetraploid cytotype was thought to exist,Шаблон:Sfn but this is believed to be the result of plants occasionally producing 32 diploid (rather than 64 haploid) spores and giving rise to diploid gametophytes.Шаблон:Sfn

It is most similar in appearance to the closely related A. lumholtzii, and both are present in Sonora, but the latter has a darker leaf stalk and axes and the leaf is less highly divided.Шаблон:Sfn

Taxonomy

The species was first described in 1917 as Notholaena jonesii by William Ralph Maxon. It was named for Marcus E. Jones, who collected the material on which the description was based.Шаблон:Sfn

Both Edwin Copeland and Charles Alfred Weatherby suggested in the 1940s that a group of ferns related to Notholaena nivea might represent a distinct genus of its own.Шаблон:SfnШаблон:Sfn Weatherby thought that, until that genus was described, the group might better be placed in Pellaea, rather than in Notholaena, but died in 1949 before he could circumscribe and publish it. Accordingly, in 1950, Conrad Vernon Morton transferred the species to Pellaea as P. jonesii, to provide a name for it in Thomas Henry Kearney's Flowering Plants and ferns of Arizona.Шаблон:Sfn In 1958, Philip A. Munz, preparing a flora of California and following Copeland's opinion that Notholaena was best lumped into a broadly defined Cheilanthes, transferred it to that genus as C. jonesii.Шаблон:Sfn John T. Mickel, carrying out a similar program of lumping in 1979, accidentally duplicated Munz's combination.Шаблон:Sfn

The recognition of the N. nivea group as a genus was finally addressed in 1987 by Michael D. Windham, who was carrying out phylogenetic studies of the cheilanthoids. He elevated Notholaena sect. Argyrochosma to become the genus Argyrochosma,Шаблон:Sfn and transferred this species to that genus as A. jonesii.Шаблон:Sfn In 2018, Maarten J. M. Christenhusz transferred the species to Hemionitis as H. jonesii, as part of a program to consolidate the cheilanthoid ferns into that genus.Шаблон:Sfn

Phylogenetic studies have shown that A. jonesii is a sister species to A. lumholtzii, a rare Sonoran species; these two species form a clade sister to another clade containing A. formosa and A. microphylla.Шаблон:Sfn 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.Шаблон:Sfn

Distribution and habitat

Argyrochosma jonesii is known in the United States from California, Arizona, Nevada, and southern UtahШаблон:Sfn and in Mexico from Sonora,Шаблон:Sfn particularly within the Mojave and Sonoran Deserts. It grows on calcareousШаблон:Sfn or igneousШаблон:Sfn cliffs and ledges, at an altitude from Шаблон:Convert.Шаблон:Sfn

Conservation

Under the NatureServe conservation status system, A. jonesii is ranked as apparently secure (G4), but it is considered critically imperiled in Utah.Шаблон:Sfn

Cultivation

It prefers high light, and moist-dry to dry, well-drained soil, perhaps of high pH.Шаблон:Sfn

Notes and references

References

Шаблон:Reflist

Works cited

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External links

Шаблон:Commons category

Шаблон:Taxonbar

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