Plagiothecium lucidum (Hook.f. & Wilson) Paris

Authority

Buck, William R. 1998. Pleurocarpous mosses of the West Indies. Mem. New York Bot. Gard. 82: 1-400.

Family

Plagiotheciaceae

Scientific Name

Plagiothecium lucidum (Hook.f. & Wilson) Paris

Description

Species Description - Plants small to medium-sized in dirty pale-green, scarcely glossy, mostly thin, flat mats. Stems creeping, to ca. 8 cm long, but mostly ca. 2 cm, simple to scarcely and weakly branched, somewhat to obscurely complanate-foliate; in cross-section with a single row of medium-sized cells with thin outer walls and firm side and inner walls, subtended by single row of small firm-walled cells surrounding large thin-walled cells, central strand very small, of 2-3 small thin-walled cells; pseudoparaphyllia not seen; axillary hairs with a single short brown basal cell and (3-)4-5 elongate hyaline distal cells. Leaves closely spaced, erect to erect-spreading, often arched with downward-pointing apices, little altered when dry, narrowly ovate, (0.7-)0.85-1.5(-2.1) mm long, gradually and slenderly acuminate, symmetric, slightly concave, narrowly decurrent; margins entire or rarely with 1-2 small teeth at extreme apex, plane or more typically erect almost throughout; cells linear, subflexuose, 85-140 X 5-6(-8) µm, smooth, thin- to firm-walled, heavily chlorophyllose, not or scarcely shorter in the acumen, becoming somewhat shorter toward the insertion; alar cells few in extreme basal angles, quadrate to short-rectangular, extending into the narrow decurrencies (these occasionally stripping off with dissection) where short-rectangular, often somewhat inflated, 1-2(-3) cells wide, 3-4 cells long. Asexual propagula not seen. Autoicous. Perichaetial leaves erect, pale, oblong-ovate, 0.9-1.1 mm long, gradually acuminate; margins subentire throughout or with a few small teeth above, plane; costa none; cells linear, smooth, thin-walled, becoming shorter, broader and rectangular toward the insertion; alar cells not differentiated. Setae elongate, reddish, 0.9-17 cm long, twisted; capsules erect to horizontal, short-cylindric, 0.5-1.5 mm long, smooth; exothecial cells subquadrate to short-rectangular, firm-walled; annulus of 1-2 rows of small, thick-walled cells; operculum high-conic, ca. 0.6 mm long; exostome teeth on front surface cross-striolate below, papillose above, trabeculate at back; endostome with a high, smooth basal membrane, segments smooth or finely roughened, keeled, narrowly perforate, ca. as long as the teeth, cilia papillose, in groups of 12, nodulose, shorter than the teeth. Spores spherical, papillose, 914 µm diam. Calyptrae cucullate, naked, smooth.

Discussion

2. Plagiothecium lucidum (Hook.f. & Wilson) Paris, Index Bryol. 962. 1897; Hypnum lucidum Hook.f. & Wilson, London J. Bot. 3: 554. 1844; Hypnum lucidulum Hook.f. & Wilson ex Hook.f., Fl. Antarct. 2: 418. 1847, ortho. var.; Plagiothecium lucidulum (Hook.f.) Mitt., J. Linn. Soc., Bot. 12: 521. 1869, ortho. var. Plate 116, figures 9-16 For additional synonymy based on South American types see Buck & Ireland, 1989: 10). Discussion. Plagiothecium lucidum is characterized by slenderly acuminate leaf apices and laminai cells only about 5-6 pan wide. The decurrencies are small but nevertheless sometimes strip off with leaves on dissection. It most closely resembles the north temperate P. laetum Bruch & Schimp. but has symmetric, long-acuminate leaves with plane to erect margins, entire leaf apices, and no asexual propagula. Plagiothecium laetum, known in North America sporadically in the West and in the East around the Great Lakes east to the Canadian Maritimes and south in the Appalachians, has asymmetric, acute to short-acuminate leaves with margins narrowly recurved nearly to the apex, leaf apices often serrulate, and 3-6-celled fusiform propagula. Plagiothecium lucidum is known in the West Indies only in a small area of the high central plateau of the Dominican Republic. The area is distinctive for its numerous disjuncts, both from Andean South America as well as temperate North America.

Distribution

Range. Colombia and Venezuela to Tierra del Fuego, southeastern Brazil; Hispaniola (Dominican Republic); growing on humus, shaded soil, or rarely moist rocks, in cloud forests, in the West Indies at 1900-2100 m.

South America| Haiti South America| Dominican Republic South America|