Pterobryon densum Hornsch.

Authority

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

Family

Pterobryaceae

Scientific Name

Pterobryon densum Hornsch.

Description

Species Description - Plants robust, to 10 cm tall, in mostly dark-green, dense, epiphytic colonies. Primary stems creeping, filiform, with small, reduced leaves, turning ca. 90° and becoming the upright secondary stem (stipe), the creeping stem continuing by a bud from near the base of the stipe, stipes regularly frondose and pinnately branched, erect; in cross-section with 6-8 rows of small thick-walled reddish cells surrounding gradually larger firm-walled cells, central strand none; paraphyllia none; pseudoparaphyllia filamentous, numerous; axillary hairs with a single short brown basal cell and 2-3 elongate brown distal cells. Stipe leaves differentiated from branch leaves, pale, erect-appressed from a clasping base, oblong-lanceolate, ca. 3 mm long, gradually acuminate, not plicate, decurrent; margins subentire throughout or with a few small apical teeth, plane; costa single, faint, ending near midleaf; cells linear, smooth, very thick-walled, the walls and lumina ca. the same width, porose, becoming shorter, broader, and more porose toward the yellowed insertion; alar cells not differentiated but cells of the decurrencies longer than those across the insertion. Branch leaves spreading, not conspicuously ranked, little altered when dry, lanceolate, 2.9-3.5 (-5) mm long, broadly acuminate, weakly concave, plicate, short-decurrent; margins sharply serrate above, subentire below, plane; costa single, ending ca. 4/5 the leaf length, projecting as a small spine at the tip; cells linear, ca. 10:1, smooth, thick-walled, porose, becoming shorter and broader toward the yellowed insertion; alar cells not or scarcely differentiated. Asexual propagula often clustered in leaf axils, uniseriate, (3-)6-18-celled, the distal cell often hyaline, the others green. Dioicous. Perichaetia large, conspicuous; innermost leaves oblong-lanceolate, 5-6 mm long, gradually long-acuminate; margins serrulate above, entire below, plane; costa single, ending near midleaf; cells linear, smooth, thick-walled, porose, becoming wider, thicker-walled, and more porose at the yellowed insertion. Setae short, smooth, ca. 0.5 mm long; capsules immersed, broadly cylindric, erect and symmetric, ca. 2 mm long, thickened and shiny at the mouth; exothecial cells irregularly hexagonal, firm-walled; annulus of inflated cells, early deciduous (fide A. Newton, in litt., 19 Jan 1996); operculum conic-rostrate, the rostrum somewhat oblique and ca. 0.4 mm long; exostome teeth not bordered or shouldered, unornamented to finely roughened, not perforate, with a prostome, not trabeculate at back; endostome inconspicuous. Spores spherical, smooth or finely roughened, 2845 µm diam. Calyptrae mitrate, with a few coarse lobes at base, naked, smooth.

Discussion

1. Pterobryon densum Hornsch. in Mart., Fl. Bras. 1(2): Cham., Linnaea 6: 62. 1831, nom. nud.; Pilotrichum 51. 1840; Crxptothecia densa Hornsch. ex Schltdl. & hornschuchii Müll. Hal., Syn. Musc. Frond. 2: 179. 1851, non Pilotrichum clensum (Hedw.) Müll. Hal., Syn. Musc. Frond. 2: 160. 1850 [= Prionodon densus (Hedw.) Müll. Hal.]. Plate 51, figures 1-7 Discussion. Pterobryon densum is a large, handsome moss, known in the West Indies only from the Dominican Republic, where it is not uncommon. It is recognized by the robust stature, the plicate leaves, and the relatively strongly serrate upper leaf margins. There may be some confusion between juvenile forms (when scarcely branched) and Prionodon densus, but in that species the cells are much shorter, almost isodiametric, and papillose.

Distribution

Range. Mexico to Panama, Colombia, Venezuela, Ecuador, Peru, Bolivia, southeastern Brazil; Hispaniola (Dominican Republic); growing on tree trunks and branches, in humid hardwood forests, at 1000-2000 m.

Mexico North America| Central America| Colombia South America| Venezuela South America| Ecuador South America| Peru South America| Bolivia South America| Brazil South America| Dominican Republic South America|