Monographs Details: Pseudotrachypus
Authority: Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.
Description:Genus Description - Plants slender to medium-sized, in green to blackish, mostly extensive, pendent colonies. Stems pendent, irregularly branched, complanate-foliate; in cross-section with small thick-walled cells surrounding large thin-walled cells, central strand small; pseudopa-raphyllia broadly foliose; axillary hairs 5-8-celled with the distal cells sometimes elongate, all hyaline. Stem and branch leaves somewhat differentiated, spreading, little altered when dry, inserted in a straight line ± perpendicular to the stem, lanceolate to ovate-lanceolate, long-acuminate, concave, at base subclasping and narrowly decurrent; margins ± serrulate, sometimes undulate, plane to recurved; costa single, slender, ending above midleaf, often projecting as a small spine at apex; cells linear, unipapillose on both surfaces, thin-walled; alar cells well developed. Asexual propagula none. Dioicous. Perichaetia inconspicuous; leaves lanceolate, smaller than stem leaves, long-acuminate; margins entire, plane; costa single, sometimes almost obsolete; cells linear, smooth, firm-walled. Setae short, smooth, ± flexuose; capsules short-exserted, erect, short-cylindric; exothecial cells short-rectangular, strongly collenchyma-tous; annulus of 1-2 rows of thick-walled elongate cells, deciduous; operculum conic, short-rostrate, straight; columella cylindric, blunt, ending near midum; peristome inserted below the mouth, exostome teeth golden, on the front surface cross-striolate below, with overlying papillae, coarsely papillose above, moderately trabeculate at back; endostome with a medium-high basal membrane, segments papillose, keeled, perforate, ca. as long as the teeth, cilia rudimentary. Spores spherical, finely papillose, medium-sized. Calyptrae mitrate, naked, lightly roughened above.
Discussion:Pseudotrachypus P. de la Varde & Thér. in Thér., Mem. Soc. Cub. Hist. Nat. “Felipe Poey” 14: 357. 1940.
Barbella sect. Aerobryella M. Fleisch., Musci Buitenzorg 3: 803. 1908.
Pseudobarbella Nog., J. Hattori Bot. Lab. 2: 81. 1947.
Barbella sect. Elongatae Nog., J. Hattori Bot. Lab. 41: 329. 1976.
Discussion. Pseudotrachypus is readily distinguished in our flora by the often blackish, complanate-foliate, pendent plants whose leaves are acuminate and undulate. The costa is single and the laminal cells are unipapillose.
In the New World Pseudotrachypus has primarily been confused with Aerobryopsis. However, in Aerobryopsis the laminal cells are shorter and much thicker-walled. The generic name Pseudotrachypus has scarcely been used since its description. However, when our single species (but with multigeneric placements) is excluded from Aerobryopsis and Barbella, Pseudotrachypus provides the oldest name for a group of species, primarily Asian, that deserves generic segregation. In Asia the genus has mostly gone under the name Pseudobarbella, but Pseudotrachypus has priority.