Platygyrium fuscoluteum Cardot 1910

Platygyrium fuscoluteum

Platygyrium fuscoluteum Cardot, Rev. Bryol. 37: 49. 1910. Type: Mexico. Chihuahua: environs de Madera, 1908, Palmer 445 p.p. (holotype: NY!).

Regmatodon fusco-luteus Schimp. ex Besch., Mém. Soc. Sci. Nat. Cherbourg 16: 232. 1872; Platygyrium fuscoluteum (Besch.) Cardot, Rev. Bryol. 38: 40. 1911, hom. illeg., non Cardot, 1910. Type: Mexico. Orizaba, F. Müller (holotype: BM!).

Plants in relatively robust mats, yellowish brown. Stems to ˜5 cm long, irregularly to regularly 1–2-pinnately branched, in cross section without a hyalodermis, central strand lacking; branches 3–10 mm long, rarely longer, straight to curved; axillary brood branchlets occasionally near branch tips. Leaves mostly 1.3–1.6 mm long, 0.3–0.4 mm wide, oblong-lanceolate, acuminate, usually homomallous but sometimes straight, slightly plicate; margins entire, conspicuously recurved in lower half, sometimes almost to leaf apex; median cells mostly 50–75 × 4–6 μm, slenderly elongate; alar cells 5–12 up the margins, subquadrate, sometimes colored. Perichaetial leaves oblong-lanceolate, acuminate, ± plicate; margins serrulate above. Setae 8–20 mm long, reddish. Capsules 2–2.5 mm long, pale yellow-brown, cylindrical, nearly symmetric; operculum slenderly and mostly obliquely long-rostrate. Annulus of 1–2 rows of cells. Exostome teeth cross-striolate below, smooth to lightly roughened above, strongly trabeculate at back; endostome segments brownish, smooth; cilia rudimentary, single. Spores 15–20 μm in diameter, finely granular. Calyptra 2.0–2.5 mm long.

Distribution and ecology: Mexico; also in the southwestern United States; occurring on tree trunks and logs, rarely on soil in coniferous and deciduous forests at altitudes of 2200–2800 m.

Illustrations in publications: Pl. 751 in Ando (1994: 1011).

Discussion: This species is confined to Mexico and the southwestern United States (Arizona, New Mexico, and Texas). It mostly occurs at higher elevations on tree trunks and logs in hardwood and mixed conifer-hardwood forests at 1300–2500 m. The glossy yellowish brown plants with homomallous leaves and long, slender apices on elongate branches are characteristic. The strongly recurved leaf margins and somewhat plicate leaves, coupled with subquadrate alar cells, make the species distinctive. The axillary brood branchlets are less conspicuous and less common than in the more northerly P. repens, but they are usually present.

Homomallium mexicanum Cardot is similar to P. fuscoluteum. As mentioned above, the capsules (if the plants are fertile) in Homomallium are curved. Vegetatively, the two may be separated by the brood branchlets in Platygyrium and by the homomallous leaves in Homomallium. From Pylaisia, Platygyrium fuscoluteum can be separated by the straight branches and straight to mildly homomallous leaves, in addition to the brood branchlets; some Pylaisia species have curved branches and strongly homomallous to falcate leaves.

Specimens examined: MEXICO. Coahuila: Maderas del Carmen, 2500 m, Riskind 1990a (NY). Michoacan: Between Chilchota and Zacapu, 2135 m, Weber & Charette B-9854 (NY). Veracruz: Just S of the city of Xalapa, Rancho Guadeloupe, 1300 m, Buck 35323 (NY). Zacatecas: Sierra de los Morones, 37 km W de Jalpa, Cárdenas 845 (MEXU, NY).

Platygyrium fuscoluteum là một loài Rêu trong họ Hypnaceae. Loài này được Cardot miêu tả khoa học đầu tiên năm 1910.