Английская Википедия:Argyrochosma incana

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Шаблон:Short description Шаблон:Speciesbox 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 (the "false cloak ferns") in 1987, recognizing their distinctness from the "cloak ferns" (Notholaena sensu stricto).

Description

Argyrochosma incana is a medium-sized epipetric fern. The rhizome is short, thick, and may be horizontal or somewhat upright. It bears linear to lanceolateШаблон:Sfn or linear-ligulate (straplike) scalesШаблон:Sfn Шаблон:Convert long and Шаблон:Convert wide, without teeth at the marginsШаблон:SfnШаблон:Sfn and long-attenuate at the tip.Шаблон:Sfn They are of a uniform dark, shiny brown,Шаблон:Sfn chestnut-brownШаблон:Sfn or yellowish-brown color with some dark brown patches.Шаблон:Sfn From the rhizome, the fronds arise in clumps. From base to tip of leaf, they are Шаблон:Convert long,Шаблон:Sfn sometimes up to Шаблон:Convert.Шаблон:Sfn Of this length, about half is made up by the stipe (the stalk of the leaf, below the blade), which is shiny and round, hairless, and dark purple to black in color, occasionally chestnut-brown.Шаблон:SfnШаблон:Sfn It is typically Шаблон:Convert in lengthШаблон:Sfn and Шаблон:Convert in diameter.Шаблон:Sfn

The leaf blades are deltate (triangular)Шаблон:Sfn or lanceolate,Шаблон:Sfn tripinnate (cut into pinnae, pinnules and pinnulets) to almost quadripinnate at their bases. They are Шаблон:Convert wide, occasionally as little as Шаблон:Convert,Шаблон:Sfn obtuse (blunt) at the base and acute (pointed) to acuminate at the tip.Шаблон:Sfn The rachis (leaf axis) is round or slightly flattened.Шаблон:Sfn 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.Шаблон:Sfn Each blade bears 6 to 9 pairs of pinnae, borne oppositely, or nearly so, on the rachis.Шаблон:SfnШаблон:Sfn They are deltate to ovate in shape and borne on long stalks.Шаблон:Sfn The ultimate segments of the blade are broadly oblong to ovateШаблон:Sfn or elliptic in shape, Шаблон:Convert long, occasionally as little as Шаблон:Convert,Шаблон:Sfn broadly obtuse at their tips and truncate or subcordate (nearly heart-shaped) at their bases.Шаблон:Sfn The leaf tissue is grayish-green in colorШаблон:Sfn and leathery in texture.Шаблон:SfnШаблон:Sfn The underside of the leaf is coated in white farina (powder), which may be sparsely scattered on the upper surfaceШаблон:Sfn or absent from it.Шаблон:SfnШаблон:SfnШаблон:Sfn The leaf axes curl upwards when dry.Шаблон:Sfn

The sori lie along the veins, forming a band Шаблон:Convert wide,Шаблон:Sfn occupying from two-thirds to the entire length of the veins.Шаблон:Sfn The veins themselves tend to blend into the leaf tissue.Шаблон:Sfn The leaf edges are not curved under or modified into false indusia. Each sporangium bears 64 spores. The plants are diploid, with a chromosome number of 2n = 54.Шаблон:SfnШаблон:Sfn

Within the heart of its range, in Mexico, A. incana is both the most widespread member of the genus and the most variable.Шаблон:Sfn Some of the characteristics observed to vary are the size of segments (reduced to Шаблон:Convert wide), the density of farina on the upper surface, the shape and color of the blade axes (zig-zag rather than straight, and dark purplish rather than black), and the joint at the base of leaf segments (more sharply defined). Material collected in several states of northern Mexico, with small segments, somewhat zig-zag and dark purplish axes may represent an as yet undescribed species.Шаблон:Sfn Two specimens collected by C. H. Müller and his wife Mary in Nuevo Leon are anomalous in having chestnut-brown axes and rougher spores, similar to A. delicatula, but their size, abundance of farina below, and lack of it above, led Maxon and Weatherby to classify them as A. incana.Шаблон:Sfn

In Mexico, A. incana closely resembles A. delicatula, from which it is distinguished by having white (rather than pale yellow) farina,Шаблон:Sfn and A. formosa, which lacks farina.Шаблон:Sfn Most specimens in the United States were originally mislabeled as A. limitanea, but this species lacks the joint and abrupt end of dark color at the base of its leaf segments.Шаблон:Sfn

Taxonomy

It was first described in 1825 by Carl Borivoj Presl as Notholaena incana, based on material collected by Thaddäus Haenke in Mexico.Шаблон:SfnШаблон:Sfn He did not explain why he chose the species epithet incana, meaning "hoary" (grayish-white).Шаблон:Sfn In 1859, Mettenius recognized the genus Gymnogramma for species where sporangia were borne along the nerves and not densely clustered at the end of the nerves.Шаблон:Sfn He independently described the species based on material collected by Eugénio Schmitz in Mexico, naming it G. candida. The epithet refers to the chalk-white color of the farina beneath the leaves.Шаблон:SfnШаблон:Sfn Prantl expanded Pellaea to include several genera in which he perceived close affinities, including Gymnogramma. Accordingly, he transferred G. candida to Pellaea section Cincinalis as P. candida in 1882.Шаблон:Sfn

William Ralph Maxon and Charles Alfred Weatherby placed N. incana within a group of ferns closely related to Notholaena nivea.Шаблон:Sfn Both Edwin Copeland and Weatherby suggested in the 1940s that this group of ferns might represent a distinct genus of its own.Шаблон:Sfn 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,Шаблон:Sfn and transferred this species to that genus as A. incana.Шаблон:Sfn Meanwhile, John Mickel and Joe Beitel had transferred the species to Cheilanthes as C. incana in their monograph on the ferns of Oaxaca, which was published in 1988;Шаблон:Sfn Mickel and Alan R. Smith recognized Argyrochosma in 2004 when preparing a fern flora of Mexico.Шаблон:Sfn In 2018, Maarten J. M. Christenhusz transferred the species to Hemionitis as H. incana, as part of a program to consolidate the cheilanthoid ferns into that genus.Шаблон:Sfn

While the distinctness of A. delicatula from A. incana has been questioned in the past,Шаблон:Sfn phylogenetic studies have upheld the separation of the two taxa.Шаблон:Sfn It lies within a subclade of the genus that also contains A. incana, A. pallens, 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.Шаблон:Sfn

Distribution and habitat

Argyrochosma incana is known from New Mexico and ArizonaШаблон:SfnШаблон:Sfn south through most of the states of Mexico to Guatemala,Шаблон:Sfn and also as a disjunct in the Dominican Republic.Шаблон:Sfn David Lellinger reports a specimen (Gómez 7156, CR) collected in Costa Rica, although this occurrence is not mentioned in other floras.Шаблон:Sfn

In Mexico, it grows on rocky slopes, banks, and ledges, often shaded or in woods, especially pine-oak forests. It is found at an altitude from Шаблон:Convert.Шаблон:Sfn Irving Knobloch reported that material collected from rock crevices in Chihuahua was growing in neutral soils within the crevices.Шаблон:Sfn At the northern edge of its range, in the United States, it is found growing from canyon walls, exclusively on igneous rock.Шаблон:Sfn In Guatemala, it is found on both shaded and sunny rocks, and growing from rock walls and cliff crevices.Шаблон:Sfn

Conservation

Under the NatureServe conservation status system, A. incana is ranked as secure (G5), but it is considered imperiled in Arizona.Шаблон:Sfn

Notes and references

References

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Works cited

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