Plagiothecium

• Authority

  Buck, William R. & Ireland, Robert R. 1989. Plagiotheciaceae. Fl. Neotrop. Monogr. 50: 1-23. (Published by NYBG Press)

• Family

  Plagiotheciaceae

• Scientific Name

  Plagiothecium

• Type

  Type. Plagiothecium denticulatum (Hedwig) Bruch, Schimper & Gümbel.

• Synonyms

  Philoscia, Acrocladiopsis, Plagiotheciella, Saviczia

• Description

  Genus Description - Plants often glossy, in dark green to yellow-green, sometimes whitish green, thin to dense, flat mats. Stems 1-10 cm long, usually complanate-foliate, sometimes subjulaceous to junceous, often stout, simple or sparsely and irregularly branched; in cross-section with a cortex of a single row of large, thin-walled cells, subtended by smaller, thicker-walled cells, internally with large, thin-walled cells, central strand present or indistinct; pseudoparaphyllia foliose, rare; axillary hairs with a single, short, brown basal cell and three to four elongate, hyaline apical cells. Stem and branch leaves similar, ovate, ovate-lanceolate, oblong-lanceolate, or oblong-ovate, often concave, acute, acuminate or piliferous, soft, imbricate to distant, erect or spreading, sometimes secund, little altered when dry, symmetric or often asymmetric, smooth or undulate, strongly or scarcely decurrent; margins plane or recurved, entire or serrulate to serrate at extreme apex; costae short and double, one branch often reaching 1/3-½ the leaf length, rarely one branch poorly developed and costa appearing single, or costa sometimes lacking; upper cells linear, linear-flexuose or sometimes, when exceptionally broad, linear-rhomboidal, often becoming shorter near leaf apex and toward insertion, smooth or rarely with minute, granular, cuticular roughenings; alar cells often differentiated; decurrencies triangular to auriculate, in one to several vertical rows, cells elongate to rounded-quadrate. Brood-bodies often present (but not in South American taxa) from a stalked, branched base, cylindrical or fusiform, 2-7-celled, uniseriate, clustered in leaf axils on stems and branches, sometimes on dorsal leaf surfaces, hyaline to light green. Autoicous or dioicous. Perichaetia and perigonia numerous at bases of stems; perigonial bracts short, lanceolate to ovate, acuminate to filiform-acuminate; perichaetial leaves moderately enlarged, sheathing with somewhat spreading apices. Setae smooth, long, twisted, straight, curved or rarely circinate, yellow, orange to red-brown; capsules erect to cemuous, rarely pendulous, straight or arcuate, yellow, orange to red-brown, oblong to ovoid, often contracted under mouth when dry, smooth to furrowed; exothecial cells thick- or thin-walled; annulus differentiated in 1-3 rows, deciduous, sometimes tardily so; operculum conicto rostrate, shorter than the urn; exostome teeth bordered, shouldered, on outer surface cross-striolate below, sometimes with overlying papillae, coarsely papillose above, rarely papillose throughout, projecting from inner surface; en-dostome papillose, with a mostly high basal membrane, segments keeled, not or very narrowly perforate, cilia 1-3, nodulose, as long as or nearly as long as the segments, rarely rudimentary or lacking. Spores spherical to ovoid, smooth or papillose. Calyptrae cucullate, smooth, naked, fugaceous.

• Discussion

  Distribution and Ecology: Plagiothecium is a genus of about 80-90 species predominantly occurring in the temperate zones. Its incursion into the tropical latitudes is primarily at higher elevations. The genus is best recognized by its mostly complanate stems with decurrent leaves. The costa is short and double and the mostly linear laminal cells are heavily chlorophyllose.