Platygyriella pringlei W. R. Buck 1984

Platygyriella pringlei

Platygyriella pringlei (Cardot) W. R. Buck, Brittonia 36: 87. 1984a; Erythrodontium pringlei Cardot, Rev. Bryol. 37: 11. 1910; Bryosedgwickia pringlei (Cardot) Bizot & P. de la Varde, Rev. Bryol. Lichénol. 21: 10. 1952. Type: Mexico. Michoacán: Coru, 1907, Pringle 10438 p.p. (lectotype: PC!; isolectotypes: CANM!, FH!, US!, both types designated by Buck, 1984a).

Erythrodontium densum var. brevifolium Cardot, Rev. Bryol. 37: 12. 1910; Bryosedgwickia densa var. brevifolia (Cardot) Bizot & P. de la Varde, Rev. Bryol. Lichénol. 21: 10. 1952. Type: Mexico. Michoacán: Coru, 1907, Pringle 10438 p.p. (holotype: PC!; isotypes CANM!, FH!, NY!, US!).

Erythrodontium imbricatifolium R. S. Williams ex Cardot, Rev. Bryol. 37: 12. 1926; Platygyriella imbricatifolia (Cardot) Thér., Smithsonian Misc. Collect. 78(2): 27. 1926. Type: Mexico. Jalisco: Barranca de Guadalajara, Pringle 709 (holotype: PC; isotypes: FH!, NY!).

Plants moderately robust in mostly dense mats, brownish, rather shiny. Stems to ˜10 cm but usually about half that, irregularly branched; stems in cross section with (2–)3–5 rows of small, thick-walled cells surrounding abruptly larger, thinner-walled cells, central strand lacking; branches prostrate, slightly curved, terete; pseudoparaphyllia filamentous; axillary hairs with 1(–2) short, brown basal cell(s) and 4–5 elongate, hyaline apical cells. Asexual reproduction rarely by flagellate branches with greatly reduced leaves. Leaves 0.9–1.2 mm long, imbricate, concave, ovate, abruptly acuminate; margins entire to minutely serrulate, erect; costa short and double; cells linear, not shorter in the apex; alar cells quadrate to oblate, rarely reaching the costa; the decurrencies of mostly 3–6 somewhat enlarged cells in 1–2 rows. Dioicous. Setae ˜2 cm long, red; capsules 3–4 mm long; operculum short-rostrate; cells at mouth of urn rarely tardily deciduous (not forming a true annulus); exostome teeth light yellow, cross-striolate below, smooth to faintly papillose at the extreme apex; endostome with a moderately high basal membrane; segments narrow, ± keeled, smooth to lightly papillose, cilia none. Spores 14–19 μm in diameter.

Distribution and ecology: Mexico (where it is relatively common) and Guatemala; usually occurring on sunny rocks, less often on trunks of deciduous trees, commonly in oak-pine forests, above 2000 m.

Illustrations in publications: Fig. 162A, B in Bartram (1949: 365); Pl. 758 in Buck (1994: 1021).

Discussion: This is a very attractive moss, with a beautiful brownish coloration. It can be distinguished from P. densa by its rupestral habitat, greater stature, imbricate and abruptly tapered leaves, and larger decurrencies with less markedly differentiated cells. There are peristomial features separating the two as well, but neither is commonly found fertile. Confusion is more likely with Erythrodontium longisetum (Hook.) Paris. However, in Erythrodontium longisetum the leaves are oblong rather than ovate, the decurrencies are quite broad, the inflorescences are autoicous, and the setae are yellow rather than red. Erythrodontium densum var. brevifolia, characterized only by flagellate branches, is a rare and unimportant expression of the species.

Selected specimens examined: MEXICO. Chihuahua: N of Barranco de Batopilas between Divisaero and Quirire, Bye 6346d (COLO, NY). Durango: Below Salto, 2532 m, Sharp 1826 (NY, TENN). Guerrero: Near Taxaco, Welch 20364 (MICH, NY). Jalisco: Guadalajara, Pringle, Plantae Mexicanae 15074 (US); 14 km al W de Cuautla, por la brecha Ayutla–Mascota, Guzmán 912 (MEXU, NY). México: Mpio. Ocuilán, Barranca de Mexicapa, Km 14 on road from Sta. Mónica de Ocuilán to Cuernavaca, 18°58'N, 99°20'W, 2200–2350 m, Buck 28137 (NY). Michoacán: 6 km NE of Zinapécuaro, 19°54'N, 100°47'W, 2020 m, Delgadillo 4980 (MEXU, NY); vicinity of Morelia, Jesús del Monte, 2000 m, Arsène 7602, 7603, 7606, 7618, 7624 (US); Carríndapaz, 2100 m, Arsène 7702, 7953 (US); Cerro San Miguel, 2200 m, Arsène 5101 (US); Bosque San Pedro, 1950 m, Arsène 4584 (US). Morelos: oberh. D. neuen Autobahn zw. Cuernavaca u. Mexico City, 2050–2100 m, Düll 199 (MICH, NY). Oaxaca: 22.4 km N on Hwy. 175 from jct. with Hwy. 190, near La Punte, NE of Oaxaca, 17°12'N, 96°05'W, 2532 m, Vitt 17624 (ALTA, NY). Puebla: Honey Station, Pringle 15128 (US); Zacatlán, Orcutt 1262 (NY). San Luis Potosí: Above Xilitl, 763 m, Sharp 5906 (NY,TENN). Sinaloa: Along Hwy. 40, ˜3 km E of Las Palmitas, 2288 m, Norris 20598 (NY, TENN). GUATEMALA. Quetzaltenango: Mpio. Zunil, road to Fuentes Georginas, 4 km S of Zunil, NW slopes of Volcán Zunil, 14°45'N, 91°29'W, 2442 m, Quedensley 2140 (BIGU, NY).