Homalothecium

• Authority

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

• Family

  Brachytheciaceae

• Scientific Name

  Homalothecium

• Description

  Genus Description - Plants slender to robust, in often lustrous, yellowish to brown or green mats. Stems creeping to ascending, freely and densely, irregularly to pinnately branched, the branches often curved; in cross-section with small thick-walled cells surrounding larger thinner-walled cells, central strand typically well developed; paraphyllia none; pseudoparaphyllia foliose; axillary hairs with a single short brown basal cell and 1-4 relatively short hyaline distal cells. Stem and branch leaves not or scarcely differentiated, crowded, ± erect when dry, ± erect-spreading when moist, mostly lanceolate, sometimes ovate, acuminate, sometimes hairpointed, often concave, plicate, not to distinctly decurrent; margins entire to serrulate throughout, plane to recurved below; costa single, ending (1/2-)2/3-3/4 the leaf length; cells long-oval to linear, often flexuose, smooth or prorulose, firm- to thick-walled, porose or not; alar cells well differentiated, subquadrate. Asexual propagula none. Dioicous or phyllodioicous. Perichaetia conspicuous; leaves erect, lanceolate, acuminate, ± plicate; margins often serrulate, mostly plane; costa single, weaker than in vegetative leaves; cells linear, smooth, firm-walled, ± porose, becoming subquadrate to rectangular toward the insertion; alar cells not differentiated. Setae elongate, ± roughened throughout, reddish or orange; capsules erect and symmetric (Homalothecium s.str.) to inclined and ± arcuate (Camptothecium), cylindric, smooth; exothecial cells subquadrate to short-rectangular, firm- to thick-walled, not collenchymatous, stomata round-pored; annulus differentiated; operculum conic to obliquely rostrate; columella slender, exserted from mouth; exostome teeth reddish brown, triangular, ± shouldered, narrowly bordered, on the front surface cross-striolate below, papillose above, trabeculate at back; endostome with a low to high basal membrane, segments papillose, keeled, mostly perforate, cilia well developed and nodose to rudimentary or absent. Spores spherical, finely papillose. Calyptrae cucullate, naked or ? hairy, smooth.

• Discussion

  Homalothecium Bruch & Schimp. in Bruch, Schimp. & W. Gümbel, Bryol. Eur. 5(fasc. 46-47, Monogr. 1): 91. 1851; Hypnum sect. Homalothecium (Bruch & Schimp.) Müll. Hal. ex C. Mohr, Bull. Torrey Bot. Club 5: 34. 1874. Camptothecium Schimp. in Bruch, Schimp. & W. Gümbel, Bryol. Eur. 6(fasc. 52-54, Monogr. 1): 31. 1853; Hypnum sect. Camptothecium (Schimp.) Lesq., Mem. Calif. Acad. Sci. 1: 32. 1868. Discussion. Homalothecium is characterized by mostly lanceolate, plicate leaves with well-developed alar cells. The setae are roughened and the capsules are erect and symmetric to inclined and arcuate. In our flora there is possible confusion only with Palamocladium, but in that genus the setae are smooth. In a more practical way, the plants of P. leskeoides are much larger (leaves ca. 3 mm long) than those of H. luteolum (leaves less than 1 mm long). We have but a single species and that may actually represent nothing more than a mislabeled specimen.