Platygyriella densa (Hook.) W.R.Buck

  • Authority

    Sharp, Aaron J., et al. 1994. The Moss Flora of Mexico. Part Two: Orthotrichales to Polytrichales. Mem. New York Bot. Gard. 69 (2)

  • Family

    Hypnaceae

  • Scientific Name

    Platygyriella densa (Hook.) W.R.Buck

  • Description

    Species Description - Plants rather small, in mostly dull, green to golden mats, Stems elongate, irregularly branched, the branches prostrate, short; flagellate branches sometimes present. Leaves erect-spreading wet or dry, lanceolate to lanceolate-ovate, concave, gradually acuminate, 0.35-0.8 mm long; margins plane or sometimes reflexed, entire or more often minutely sermlate almost throughout; costa short and double; cells linear, rarely shorter at the apex; alar cells quadrate to short-rectangular, usually extending to the costa, the decurrencies usually of 1-2 greatly enlarged cells. Dioicous. Setae 1.2-1.5 cm long; capsules ca. 2 mm long; operculum short- to high-conic; exostome teeth orange, Striolate to papillose below, smooth or faintly papillose above; endostome with a moderately high basal membrane, with walls sometimes very thickened, and narrow, flat, finely to coarsely papillose segments, cilia none. Spores 13-20 µm.

  • Discussion

    Fig. 757

    P. densa (Hook.) Buck, Brittonia 36: 86. 1984.

    Leskea densa Hook, in Kunth, Syn. Pl. l: 61.1822.

    Entodon densus (Hook.) Mitt., J. Linn. Soc, Bot. 12:531.1869.

    Platygyrium guatemaliense Schimp. ex Jaeg., Ber. Thatigk. St. Gallischen Naturwiss. Ges. 1876-77: 276. 1878, nom. nud.

    Entodon pallidissimusC. Müll., Linnaea 42: 494. 1879.

    Erythrodontium pallidissimum(C. Müll.) Par., Index Bryol. 437. 1896.

    Platygyriella helicodontoides Card., Rev. Bryol. 37: 9. 1910.

    Erythrodontium subdensum Broth. & Ther. ex Ther., Rec Publ. Soc. Havraise fitudes Diverses 88: 313. 1921.

    Bryosedgwickia densa (Hook.) Biz. & P.-Varde, Rev. Bryol. Lichenol. 20: 246. 1951.

    B. subdensa (Broth. & Ther. ex Ther.) Biz. & P.-Varde, Rev. Bryol. Lichenol. 21: 10.1952.

    B.pallidissima (C.Mull.) Biz. & P.-Varde, Rev. Bryol. Lichenol. 21: 10. 1952.

    This moss of little character is most often very small, sterile, and weather-worn in appearance. It differs from other species ofsmall size by its ovate-lanceolate, gradually tapered leaves and short, double costa, and one or two greatly enlarged, decurrent cells (which typically remain attached to the stem on dissection). The moderately high basal membrane of the endostome, which is coarsely papillose and often has strikingly thick walls, and narrow, flat segments, arc unmistakable. There is little chance of confusion with P. pringlei, which has much larger, imbricate, and more or less abruptly tapered leaves and usually several enlarged cells in the decurrencies, as well as a rupestral habit.

  • Distribution

    Usually on tree trunks, apparently common; Chiapas, Chihuahua, Distrito Federal, Durango, Guerrero, Hidalgo, Jalisco, Mexico, Michoacan, Morelos, Nayarit, Oaxaca, Puebla, Sinaloa, Tamaulipas, Veracruz.—Mexico to northern South America; reported from Haiti.

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