Pylaisia polyantha W. P. Schimper ex B. S. G. 1851

Pylaisia polyantha

Pylaisia polyantha (Hedw.) Schimp. in Bruch, Schimp. & W. Gümbel, Bryol. Eur. 5: 89. 1851; Leskea polyantha Hedw., Sp. Musc. Frond. 229. 1801; Hypnum polyanthum (Hedw.) Dicks., Fasc. Pl. Crypt. Brit. 4: 17. 1801; Pterogonium polyanthos (Hedw.) Muhl., Cat. Pl. Amer. Septentrionalils 98. 1813; Isothecium polyanthum (Hedw.) Spruce, Musci Pyren. 79. 1847; Stereodon polyanthos (Hedw.) Mitt., J. Proc. Linn. Soc., Bot., Suppl. 1: 94. 1859; Pylaisiella polyantha (Hedw.) Grout, Bull. Torrey Bot. Club 23: 229. 1896. Type: Ad truncos arborum annosarum, maxime salicum remotius ab earum basi in Germania, Anglia (lectotype: G, designated by Geissler in Margadant and Geissler, 1995).

See Arikawa (2004) for additional synonymy based on non–Latin American types.

Plants rather small, in low mats, glossy, yellow-green to bright green. Stems to 2 cm long, prostrate, regularly pinnately branched, the branches to 1 cm long, usually creeping, rarely ascending and curved. Leaves mostly straight, ovate-lanceolate, gradually long-acuminate, stem leaves 1.3–2.0 mm long, 0.4–0.5 mm wide, branch leaves 1.1–1.4 mm long, 0.3–0.5 mm wide, concave, slightly plicate; margins plane or slightly involute above, serrulate above; costa short and double; median cells 50–80 × 4–5 µm, linear; alar cells subquadrate to short-rectangular, extending up the margins by 8–10 cells, in 5–8 rows across the insertion. Perichaetial leaves to 1.4 mm long, oblong-lanceolate, abruptly short-acuminate; margins serrulate at shoulders. Setae 10–18 mm long, yellow- to red-brown, sinistrorsely twisted in lower 3/4 to 4/5 and dextrorsely twisted in upper 1/4 to 1/5 when dry; capsules 1.6–2.2 mm long, long-cylindrical, reddish brown; operculum obliquely conic; exostome teeth ˜200 µm long, smooth below, finely papillose above; endostome free, with a well-developed, smooth, basal membrane, endostome longer than the exostome teeth, papillose, keeled, not perforate, cilia single, rudimentary. Spores 11–14 µm in diameter, finely papillose.

Distribution and ecology: Pan North Temperate, extending into eastern Mexico (Nuevo Léon, San Luis Potosí, Veracruz); occurring throughout North America, also in Europe, northern and central Asia, China, Japan, and Africa; growing on tree trunks at 2500–3600 m.

Illustrations in publications: Pl. 754 (as Pylaisiella polyantha (Hedw.) Grout) in Ando (1994: 1015); Fig. 16 in Arikawa (2004: 94); Fig. 560A–G in Crum and Anderson (1981: 1137); Pl. 343 in Ireland (1982: 600).

Discussion: This North Temperate species just barely makes it into the Neotropics. It is characterized by a moderate number of alar cells (intermediate number between P. selwynii and P. falcata), a free endostome with nonperforate segments, and small spores. Its branches are not ascending and curved as in P. selwynii, and the leaves are not falcate as in P. falcata.

Specimen examined: Mexico. Nuevo León: Main road up Cerro Potosi, just below summit, ˜17 km NW of Galeana, 3600 m, 26 Jul 1985, Whittemore 2721 (MO).