Macromitrium punctatum (Hook. & Grev.) Brid.
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Authority
Sharp, Aaron J., et al. 1994. The Moss Flora of Mexico. Part Two: Orthotrichales to Polytrichales. Mem. New York Bot. Gard. 69 (2)
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Family
Orthotrichaceae
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Scientific Name
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Description
Species Description - Plants slender to robust, olive- or sometimes light-green above, rusty-brown below, in loose, spreading mats. Stems irregularly creeping, tomentose, with ascending to erect branches up to 5 cm high, pentagonal in section. Leaves variously twisted-contorted, many individual leaves spirallycontorted and spreading when dry, spirally 5-ranked, flexuose, recurved to wide-spreading, often with erect apices when moist, (1-) 1.2-3 mm long, keeled, lanceolate to narrowly ovate-lanceolate, sharply acute to broadly acuminate, often ending in a broad apiculus; margins broadly reflexed, ± serrulate to irregularly sharply serrate in the upper half; costa ending in the apex or shortly excurrent; upper cells 10-14 µm, smaller at the margins, rounded to hexagonal-rounded, elliptic near the apex, ± clear, bulging to bulging-papillose, thin-walled, with the upper and lower walls very thick; basal cells narrowly rectangular, smooth or rarely with a few low papillae, with sinuose lumina, ± thick-walled, a few thin-walled cells forming a basal border. Pseudautoicous (dwarf male plants not seen). Perichaetial leaves erect to flexuose-twisted, 3-6 mm long, narrowly lanceolate, long-subulate; margins entire or sparsely toothed at the apex; costa filling most ofthe subula and ending at the apex; cells elongate and smooth. Setae 3-8.5 mm long, smooth; capsules 1.1-2 mm long, ovoid-obovoid or oblong-ovoid to obovoid, smooth or lightly 8-ribbed with a small mouth when old; annulus of 1-2 rows of thin-walled, hyaline cells; exothecial cells ± quadrate to elongate-elliptic, variable in shape, 1-2:1, thick-walled; stomata uncommon, in the neck; exostome of 16, well-developed, truncate teeth, about 12 cells high, forming a conic membrane, densely papillose, the outer layer very thick, broken into irregular teeth and slightly recurved when old; endostome of a sparsely to densely papillose, hyaline membrane as high as the exostome. Spores anisosporous, 17-18(-21-)25-30 µm. Calyptrae sparsely to densely hairy, covering the entire capsule, very deeply laciniate (to more than 1/2), 3-4 mm long.
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Discussion
Fig. 472
M. punctatum (Hook. & Grev.) Brid., Bryol. Univ. 1: 739. 1826.
Orthotrichum punctatum Hook. & Grev., Edinburgh J. Sci. 1: 119. 1824.
Schlotheimia brachyrhyncha Schwaegr., Sp. Muse Suppl. 2(2): 53. 1826.
Macromitrium pentastichum C. Müll., Linnaea 21: 186. 1848.
M. brachyrhynchum (Schwaegr.) Schimp. ex C. Müll., Syn. Muse. Frond. 1:741. 1849.
M. pentagonum C. Müll., Malpighia 10: 513. 1896 (fide Florschutz, 1964).
M. hirtellum Bartr., Contr. U. S. Natl. Herb. 26: 86. 1928.
The species is distinguished by leaves 5-ranked (when moist) and apiculate, with large upper cells (11-14 µm ) and smooth basal cells. The perichaetial leaves are conspicuously longer than vegetative leaves and lance-subulate. The densely hairy calyptrae and smooth capsules with a well-developed double peristome are also diagnostic. The size and set of leaves are quite variable, with some collections consisting of small, stiffly ascending plants with little branching and slightly twisted leaves. Better developed specimens may have loosely spreading branches with larger twisted-contorted leaves. In spite of such variations in size, cellular features are constant. T h e upper cells have cross-walls thin and upper and lower surfaces very thickwalled and bulging, giving the cells a clear look not found in other species of the genus.
In 1824, Hooker and Greville described Orthotrichum punctatum as a species with lax, oblong-linear, acute leaves with pellucid-punctate cells; costa ending just below the apex; distinctly involute leaf set when dry; oblong-pyriform capsules; and plicate, fimbriate calyptrae. The type specimen in the Hooker herbarium (BM) consists of three stems; two are easily placed in the concept of the widespread M . pentastichum C. Mull. (1848), and the third is the same as plants presently considered under the name M . richardii Schwaegr. (1826). The earliest name I can find to use for M . punctatum sensu Mitten (1869) and Grout (1944) is M . contextum Hampe. On study of Hooker and Greville's protologue of M . punctatum, I cannot determine which portion ofthe type w as described. One capsule belongs to the "pentastichum" stem and one calyptra to the "richardii" stem. The leaves are involute in all three stems, but more strongly so in the richardii; however, the punctate nature of the upper leaves is more pronounced in the "pentastichum" stems. Thus, it appears that the description was drawn from parts of both species represented in the type. I suggested (Vitt, 1979), in accordance with Recommendation 7B of the International Code, that a lectotype be designated to preserve current usage as much as possible. In this regard, M . richardii (1826) is a well-established name for a very distinctive species; however, M . pentastichum (1848), long in use for another distinctive widespread species (by Mitten, Grout, and Florschutz, for example), must be replaced by a relatively unknown earlier name — M . brachyrhynchum Schwaegr. (1826), as its type represents the s a m e species as that of the type of M . pentastichum, not M . punctatum (M. contextum Hampe) as Mitten suggested. O n lectotypification, M . punctatum is the earhest name for the brachyrhynchum-pentastichum concept and allows the well-established name M. richardii continued use in its present context.
Additional evidence to support such typification is present in Greville's herbarium (E), where there is a Raddi specimen collected in Brazil. It consists of six stems, five of which are "pentastichum" and only one "richardii." Thus, since a majority of both the Hooker and the Greville specimens belong to the concept of "pentastichum," the original description may have been taken largely from the "pentastichum" portion.
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Distribution
On branches and trunks of trees (often on fallen branches and probably occurring in the upper portions oftrees), sometimes on rock; Chiapas, Guerrero, Hidalgo, Oaxaca, Puebla, Tamaulipas, Veracruz.—Mexico; Guatemala, Belize, Honduras, and Costa Rica; Brazil and Suriname; West Indies.
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