Plagiothecium conostegium Herzog

Authority

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

Family

Plagiotheciaceae

Scientific Name

Plagiothecium conostegium Herzog

Description

Species Description - Plants medium-sized, in lustrous, bright-green, mostly thin, flat mats. Stems creeping, to ca. 4 cm long, but often shorter, simple to sparingly and irregularly branched, complanate-foliate; in crosssection with the hyalodermis 1(-2)-layered, subtended by 1-2 rows of small firm-walled cells surrounding large thin-walled cells, central strand well developed, of small thin-walled cells; pseudoparaphyllia not seen; axillary hairs with a single short brown basal cell and 2-3 elongate hyaline distal cells. Leaves closely spaced, spreading to wide-spreading, ovate-lanceolate to narrowly oblong-ovate, 1.4-2 mm long, gradually or ± abruptly short-acuminate, somewhat asymmetric, slightly concave, conspicuously decurrent; margins subentire or with a few small teeth at extreme apex, entire below, plane or narrowly recurved below; costa short and double, sometimes extending to ca. 1/4 the leaf length; cells linear, straight or subflexuose, 110-145 X (9-) 11-15 µm, smooth, mostly thin-walled; alar cells few, poorly differentiated, rectangular, but in the decurrencies (these often stripping off with dissection) quadrate to short-rectangular, 1.5-3:1, enlarged and inflated, 2-3 cells wide, to 8 cells long. Asexual propagula not seen. Autoicous and possibly dioicous; perigonia very small in leaf axils. Perichaetial leaves erect, pale, oblong-ovate, 0.8-1.4 mm long, gradually short-acuminate; margins subentire, plane; costa none; cells linear, smooth, thin-walled, becoming shorter, broader and rectangular toward the insertion; alar cells sometimes differentiated in a single marginal row of 3-5 rounded cells. Setae elongate, smooth, reddish, 1.5-2.5 cm long, twisted; capsules inclined to horizontal, cylindric, ca. 2 mm long, usually striate or furrowed; exothecial cells subquadrate to narrowly rectangular, longer in the striations, firm- to thick-walled; annulus of 1-2 rows of small thick-walled cells, tardily deciduous; operculum high-conic, ca. 0.9 mm long; exostome teeth on the front surface cross-striolate to papillose with the papillae in horizontal rows below, papillose above, trabeculate at back; endostome finely papillose, basal membrane high, segments keeled, not or very narrowly perforate, ca. as long as the teeth, cilia papillose, in groups of 3-4, nodulose, shorter than the segments. Spores spherical, finely papillose, 10-12(-15) µm diam. Calyptrae cucullate, naked, smooth.

Discussion

3. Plagiothecium conostegium Herzog, Biblioth. Bot. 87: 154. 1916. Plate 117, figures 1-7 Discussion. Plagiothecium conostegium is distinguished by its relatively broad leaf cells (11-15 µm) and especially by large leaf decurrencies composed of short, rounded cells. The striate-furrowed capsules are also unique among the Plagiothecia of the West Indies. From sympatric P. lucidum it differs by shorter leaf acumina, broader laminal cells, and large decurrencies of shorter cells. From the relatively common P. drepanophyllum the much better developed decurrencies are the easiest way to separate the two. Some confusion might arise between P. conostegium and the north temperate P. denticulatum. However, in that species the laminal cells are even broader than those of P. conostegium (14-20 µm rather than 9-15 µm), the decurrencies are better developed, and asexual propagula are commonly produced. Like in P. conostegium, the capsules are mostly striate.

Distribution

Range. Mexico and Guatemala, Venezuela, Colombia, Ecuador, southernmost Argentina and Chile; Hispaniola (Dominican Republic); growing on humus and shaded soil, in humid forests, at 1875-3100 m.

Mexico North America| Guatemala Central America| Venezuela South America| Colombia South America| Ecuador South America| Argentina South America| Chile South America| Dominican Republic South America|