Brachythecium plumosum (Hedw.) Schimp.

  • Authority

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

  • Family

    Brachytheciaceae

  • Scientific Name

    Brachythecium plumosum (Hedw.) Schimp.

  • Description

    Species Description - Plants medium-sized, in ± lustrous, ± stiff, green to yellow-brown, dense, often small mats. Stems creeping, mostly to ca. 8 cm long, irregularly but freely branched, the branches often >1 cm long; in cross-section with 3-4 rows of small thick-walled cells surrounding abruptly larger thin-walled cells, central strand of small thin-walled cells; pseudoparaphyllia foliose; axillary hairs with a single short brown basal cell and a single elongate hyaline distal cell. Stem and branch leaves not strongly differentiated with stem leaves somewhat broader and more decurrent, branch leaves crowded, ± homomallous, erect when dry, erect-spreading when moist, oblong-lanceolate, sometimes broadly so, (1.15-) 1.4-1.9 mm long, gradually or more typically ± abruptly broadly acuminate, the apex not twisted, ± concave, not or scarcely plicate, somewhat decurrent; margins subentire to serrulate above, subentire below, plane or sometimes erect; costa single, relatively broad, tapering distally, ending somewhat above midleaf, sometimes to 2/3 the leaf length, not projecting at apex; cells linear, straight to subflexuose, smooth, firm-walled with prominent middle lamellae, not porose, becoming rhomboidal in the extreme apex, becoming broader toward the insertion; alar cells gradually but weakly differentiated in a band across the insertion, extending over the base of the costa, extending somewhat up the margins, quadrate to short-rectangular, sometimes darkened. Asexual propagula none. Autoicous. Perichaetia inconspicuous; leaves spreading from an erect base, oblong, to ca. 1.9 mm long, gradually acuminate, concave; margins ± crenulate throughout, plane; costa none; cells linear, smooth, firm-walled, ± porose, becoming shorter, broader and thinner-walled toward the insertion; alar cells not differentiated. Setae elongate, mostly slightly roughened above, rarely smooth, reddish, 0.8-1.5 cm long, straight to subflexuose, not or only slightly twisted; capsules suberect, slightly asymmetric, cylindric, ca. 1.5 mm long, dark-brown; exothecial cells quadrate to short-rectangular, thick-walled, stomata round-pored; annulus of 2 rows of small quadrate thick-walled cells, smaller than those of the exothecium, tardily deciduous; operculum obliquely short-rostrate to high-conic; exostome teeth reddish brown, triangular, scarcely shouldered, narrowly bordered, on the front surface cross-striolate below, finely papillose and pale above, trabeculate at back; endostome finely papillose, with a medium-high basal membrane, segments keeled, perforate, shorter than the teeth, cilia in groups of 1-2, very short. Spores spherical, finely papillose, 14-18 µm diam. Calyptrae cucullate, naked, smooth.

  • Discussion

    3. Brachythecium plumosum (Hedw.) Schimp. in Bruch, Schimp. & W. Gümbel, Bryol. Eur. 6(fasc. 52-54, Monogr. 1): 8. 1853; Hypnum plumosum Hedw., Sp. Musc. Frond. 257. 1801. Plate 94, figures 1-6 Hypnum flagellare Hedw., Sp. Muse. Frond. 282. 1801; Brachythecium flagellare (Hedw.) Jenn., Man. Mosses W. Pennsylvania 344. 1913. Discussion. Brachythecium plumosum is characterized by autoicous plants with homomallous, oblong-lanceolate leaves growing on wet rocks. The costa is relatively broad and the alar cells, though gradually differentiated, are well marked but not nearly as obviously so as in B. rivulare. The species is easily differentiated from the common B. ruderale by nonplicate leaves, autoicous sexuality, and setae typically roughened above. Certainly this species closely resembles Scleropodium in leaf shape and areolation, as well as sporophytic features. Like Scleropodium, B. plumosum has cells extending across the base of the costa and thus the genus needs to be either redefined or abandoned.

  • Distribution

    Range. Throughout North America, Mexico, Guatemala, northern South America, Europe, northern Africa, Asia, New Zealand, Hawaii; Jamaica, Hispaniola (Dominican Republic); usually growing on rocks, in or near streams, in the West Indies above 1500 m.

    North America| Guatemala Central America| Ecuador South America| Colombia South America| Venezuela South America| Guyana South America| Suriname South America| French Guiana South America| Brazil South America| Europe| Argentina South America| Egypt Africa| Libya Africa| Morocco Africa| Tunisia Africa| Asia| New Zealand Jamaica South America| Dominican Republic South America|