| Argyrochosma nivea | |
|---|---|
 | |
| Curtis's botanical magazine, Argyrochosma nivea var. tenera | |
Scientific classification  | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Division: | Polypodiophyta |
| Class: | Polypodiopsida |
| Order: | Polypodiales |
| Family: | Pteridaceae |
| Genus: | Argyrochosma |
| Species: | A. nivea |
| Binomial name | |
| Argyrochosma nivea | |
| Synonyms | |
| |
Argyrochosma nivea is an Andean fern species in the genus Argyrochosma .
The rhizome is short, thick, and more or less upright. It bears thin, delicate linear-subulate scales, 2.5 to 3 millimeters (0.098 to 0.12 in) long and of a uniform chestnut-brown color. The margins are entire (without teeth), or the walls of the marginal cells may project from the margin. The scales often become strongly crisped (wavy) when dried. [1]
The leaves are 10 to 30 centimeters (3.9 to 12 in) long and arise close together from the rhizome. The stipe (the stalk of the leaf, below the blade) is slender, rounded, dull (rather than shiny), lacks hairs and scales, and varies from a bright to a dark chestnut-brown. It is typically shorter than to about as long as the leaf blade. [1]
The leaf blades are lanceolate or deltate-lanceolate to ovate in shape, and tripinnate (cut into pinnae, pinnules, and pinnulets). The rachis (leaf axis) is similar in appearance to the stipe. It bears up to 12 pairs of pinnae, nearly opposite to one another, on stalks. They are ovate to lanceolate in shape. The pinnules are long and also borne on stalks. The pinnulets are broadly oblong to nearly orbicular (circular), obtuse (blunt) at the tip and truncate (abruptly cut off) to nearly cordate (heart-shaped) at the base, with entire margins. The dark color of the segment stalks stops abruptly at a joint at the base of the leaf segment. The segment at the tip of the pinnule is often lobed. The leaf tissue is leathery in texture, free of hairs and scales above and densely covered in white farina (powder) below. [1]
In fertile leaf segments, the sporangia are close to the margin, borne along the further one-half to one-quarter of the secondary veins branching from the midrib of the segment. Each sporangium contains 32 spores. The tissue of the leaf margins retains the same texture as the rest of the leaf, and is not modified into a false indusium. [1]
Isonotholaenic acid, a dihydrostilbenoid, and other bibenzyls can be found in A. nivea. [2] [3] This compound shows an anti-chagasic activity. [4]
Historically, A. flava and A. tenera have often been treated as varieties of this species. Yellow farina is the most distinctive trait of A. flava; it also differs in several more subtle characteristics, having a darker stipe and rhizome scales that are not crisped (wavy). [1] A lack of farina distinguishes A. tenera from A. nivea sensu stricto . It is also less dissected (usually only bipinnate, except at the base of the leaf blade), and has rhizome scales not strongly crisped. [1]
Another variety, Notholaena nivea var. obscura, has sometimes been distinguished from typical material, although it has no combination in Argyrochosma. It has somewhat less dissected leaves than A. niveas.s. (bipinnate to almost tripinnate at the base), more oblong ultimate segments (sometimes almost triangular and lobed), terminal segments usually entire rather than lobed, a bright chestnut-brown stipe, and rhizome scales that are not crisped. [1]
The species was first described as Pteris nivea by Jean Louis Marie Poiret in Lamarck's Encyclopédie Méthodique, Botanique in 1804. He based his description on a specimen collected in Peru by Joseph de Jussieu. [5] The specific epithet nivea, meaning "snowy", [6] evidently refers to the "snow-white" color of the farina beneath the leaves. [5] Shortly thereafter, in 1806, Olof Swartz independently described the same species as Acrostichum albidulum, based on South American material from Luis Née. [7] He distinguished Acrostichum by the presence of sporangia widely spread over the back of the leaf, rather than in discrete sori. [8] The epithet albidulum, meaning "somewhat white", presumably also refers to the presence of the white farina, which he described with the same word; [7] he credited the origin of the name to Antonio José Cavanilles, who, however, never published it. [9]
Poiret's rather wide circumscription of Pteris was subsequently narrowed by other botanists, removing cheilanthoids like P. nivea. However, delineating natural genera in the cheilanthoids has proven to be extremely difficult, and many different placements of the species were subsequently put forward. In 1811, Nicaise Auguste Desvaux revived the genus Cincinalis with his own circumscription, distinguishing it by the presence of sporangia spreading more from the margins than in Pteris but not so widely as in Acrostichum. He transferred the species there as C. nivea, and recognized A. albidulum as a synonym. [10] Problems with the application and form of the name Cincinalis led Desvaux to abandon it in 1813 in favor of Notholaena , placing the species there as N. nivea, [11] a name commonly used by other botanists for the species until the late 20th century. However, he reversed course in 1827 and moved it from Notholaena to Acrostichum as A. niveum. [12]
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. [13] He transferred the species there as G. nivea. [14] Prantl expanded Pellaea to include several genera in which he perceived close affinities, including Gymnogramma. Accordingly, he transferred G. nivea to Pellaea section Cincinalis as P. nivea in 1882. [15] Rodolfo Amando Philippi described material from the Tarapacá Region of Chile as Cincinalis tarapacana in 1891, [16] but George Hieronymus, in 1909, considered it at most a form of P. nivea. [17]
Both Edwin Copeland and Charles Alfred Weatherby suggested in the 1940s that N. nivea and a group of related ferns might represent a genus distinct from Notholaena. [18] [19] Weatherby thought that, until that genus was described, the group might better be placed in Pellaea, rather than in Notholaena, following the example of Prantl, but died in 1949 before he could circumscribe and publish it. [20]
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 , [21] and transferred this species to that genus as A. nivea. [22] In 2018, Maarten J. M. Christenhusz transferred the species to Hemionitis as H. nivea, as part of a program to consolidate the cheilanthoid ferns into that genus. [23] Meanwhile, in a 2017 treatment of Bolivian ferns, Kessler and Smith altered the circumscription of the species to exclude A. nivea var. flava and A. nivea var. tenera, elevating both to species level on the grounds of consistent differences in morphology and range and continued distinctness when growing sympatrically. [24]
It is found from Ecuador south to Argentina along the Andes. [25] [24]
It typically grows in rock crevices or on rocky soil in dry valleys, often in open areas among deciduous forest. It is found at an altitude from 1,650 to 4,500 meters (5,410 to 14,800 ft). [24]
Pteridaceae is a family of ferns in the order Polypodiales, including some 1150 known species in ca 45 genera, divided over five subfamilies. The family includes four groups of genera that are sometimes recognized as separate families: the adiantoid, cheilanthoid, pteridoid, and hemionitidoid ferns. Relationships among these groups remain unclear, and although some recent genetic analyses of the Pteridales suggest that neither the family Pteridaceae nor the major groups within it are all monophyletic, as yet these analyses are insufficiently comprehensive and robust to provide good support for a revision of the order at the family level.
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.
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".
Myriopteris lanosa, the hairy lip fern, is a moderately-sized fern of the eastern United States, a member of the family Pteridaceae. Its leaves and stem are sparsely covered in hairs, but lack scales, hence its common name. One of the cheilanthoid ferns, it was usually classified in the genus Cheilanthes until 2013, when the genus Myriopteris was again recognized as separate from Cheilanthes. It typically grows in shallow, dry, soil, often in rocky habitats.
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".
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".
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 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".
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".
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".
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".