Monographs Details: Orthotrichum
Authority: Sharp, Aaron J., et al. 1994. The Moss Flora of Mexico. Part Two: Orthotrichales to Polytrichales. Mem. New York Bot. Gard. 69 (2)
Description:Genus Description - Plants u p to 5 or rarely 13 cm high, typically olive-green above, brownish below, in cushions or tuIts on trees and rocks. Stems erect-ascending, usually forked 1-4 times. Brood bodies sometimes present on leaves. Leaves usually erect-appressed, straight, and rarely contorted-flexuose when dry, spreading to wide-spreading when moist, ovate, lanceolate, or lincar-lanccolate, obtuse to acute, rarely acuminate or piliferous, the base not clasping the stem; margins reflexed to revolute, rarely plane or involute, entire or denticulate near the apex; costa strong, usually ending near the apex; upper cells rounded-hexagonal, with thick walls and 1-3 conic or forked papillae per cell (rarely smooth); basal cells smooth, elongate-linear, thick-walled, and nodose or rectangular, thin-walled, and hyaline, grading to subquadrate near the margins. Gonioautoicous, or rarely dioicous. Perigonia large, budlike, stalked. Perichaetial leaves not or usually only slightly differentiated. Setae up to 9 mm long; capsules immersed, emergent, or exserted, 0.7-3 m m long, ovoid to cylindric, smooth, 8- or 16-ribbed, sometimes constricted below the mouth, tapering to the seta through a short neck; annulus none or poorly differentiated; stomata immersed below overarching subsidiary cells or superficial, generally in the middle and lower portions of the urn; peristome double, single, or lacking; exostome teeth 8 or 16, papillose or striate, reflexed, recurved, or erect; endostome segments 8 or rarely 16, erect to incurved, usually smooth or sometimes papillose or striate; preperistome occasionally present. Spores 9-35 µm, papillose, brown. Calyptrae oblong- or short-conic and mitrate, smooth or rarely papillose, naked or hairy, the hairs occasionally papillose, plicate, not much lobed.
Fifteen species are known from Mexico, several of them from no more than one or two localities. The saxicolous species can generally be recognized by growth in dark-green tufts, leaves imbricate and lacking hairpoints, and capsules immersed to shortly exserted and more or less ribbed. The leaf cells are roughened by simple or little-branched papillae. The calyptrae are conic-mitrate and generally hairy. The peristome is double but often reduced. The epiphytic species grow in loose or dense cushions or merely gregariously. Of these, O. diaphanum has leaves ending in hair points; O. hortoniae has long-exserted capsules; O. sharpii has crisped leaves; and the remainder (distinguished with some difficulty) have emergent capsules and imbricate leaves with papillose cells.
Reference may be made to treatments ofthe South American species by Lewinsky (1984, 1987).