Argyrochosma delicatula
Argyrochosma delicatula | |
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Scientific classification | |
Kingdom: | Plantae |
Clade: | Tracheophytes |
Division: | Polypodiophyta |
Class: | Polypodiopsida |
Order: | Polypodiales |
Family: | Pteridaceae |
Genus: | Argyrochosma |
Species: | A. delicatula
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Binomial name | |
Argyrochosma delicatula | |
Synonyms | |
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Argyrochosma delicatula is a fern known from northeastern Mexico (and from one collection in Arizona). It grows in rocky habitats, either in sun or in shade, and is distinguished from similar species by the presence of pale yellow (rather than white) powder on the underside of its leaves. First described as a species in 1939, it was transferred to the new genus
Description
Argyrochosma delicatula is a medium-sized epipetric fern. The rhizome is compact, and may be horizontal or upright.[1] It bears slender, linear to linear-subulate scales[1][2] 4 to 6 millimeters (0.2 to 0.2 in) long and 0.2 to 0.3 millimeters (0.008 to 0.01 in) wide, of a uniform orange-brown to dark brown color, with entire (toothless) margins[1] and long-acuminate at the tip.[2]
The fronds arise in clumps from the rhizome. From base to tip of leaf, they are 10 to 25 centimeters (3.9 to 9.8 in) long, occasionally as short as 6 centimeters (2 in) or as long as 35 centimeters (14 in).[1] Of this length, nearly half is made up by the stipe (the stalk of the leaf, below the blade),[1] which is shiny and round, hairless, and chestnut-brown[2] to dark purple in color.[1]
The leaf blades are
The
It is most similar to Argyrochosma incana and can be somewhat difficult to distinguish from that species. The yellow (rather than white) color of the farina, the brown to purple (rather than black) color of the axes, the narrow segments (typically 3 to 5 millimeters (0.1 to 0.2 in) in A. incana) and the presence of sparse farina on the upper surface serve to distinguish A. delicatula.[1]
Taxonomy
It was first described by William Ralph Maxon and Charles Alfred Weatherby in 1939 as Notholaena delicatula, based on material collected by Edward Palmer in Coahuila. They placed it within a group of ferns closely related to Notholaena nivea. The epithet delicatula presumably refers to what they described as the "delicate texture" of its leaves.[3] Both Edwin Copeland and Weatherby suggested in the 1940s that this group of ferns might represent a distinct genus of its own.[4] 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,[5] and transferred this species to that genus as A. delicatula.[6] In 2018, Maarten J. M. Christenhusz transferred the species to Hemionitis as H. delicatula, as part of a program to consolidate the cheilanthoid ferns into that genus.[7]
While the distinctness of A. delicatula from A. incana has been questioned in the past,
Distribution and habitat
Argyrochosma delicatula is principally known from the states of
It grows in rocky places in either sun or shade, especially on limestone ledges, and on shady slopes.[1]
Notes and references
References
- ^ a b c d e f g h i j k l m n o p q Mickel & Smith 2004, p. 65.
- ^ a b c d e f g Tryon & Weatherby 1956, p. 90.
- ^ Maxon & Weatherby 1939, pp. 7–8.
- ^ Windham 1987, p. 37.
- ^ Windham 1987, p. 38.
- ^ Windham 1987, p. 40.
- ^ Christenhusz, Fay & Byng 2018, p. 13.
- ^ a b Sigel et al. 2011, p. 561.
Works cited
- ISBN 978-0-9929993-9-1.
- JSTOR 41764097.
- 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.
- Sigel, Erin M.; JSTOR 23028975.
- JSTOR 41764632.
- Windham, Michael D. (1987). "Argyrochosma, a new genus of cheilanthoid ferns". American Fern Journal. 77 (2): 37–41. JSTOR 1547438.
External links
- Isotype of the species at JSTOR Plant Science.
- Images at plantsystematics.org (spores)