Ctenidium

• Authority

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

• Family

  Hypnaceae

• Scientific Name

  Ctenidium

• Description

  Genus Description - Plants small to medium-sized, in often lustrous, soft, green to yellow-green to yellow-brown, often extensive, dense mats. Stems creeping to ascending, irregularly to regularly pinnately branched, the branches sometimes branched, unequal, not complanate-foliate; in cross-section without a hyalodermis, with small thick-walled cells surrounding larger thinner-walled cells, central strand present; pseudoparaphyllia foliose, large; axillary hairs with 1-4 short hyaline basal cells and 1 to several mostly elongate hyaline distal cells. Stem and branch leaves differentiated, stem leaves erect-spreading to squarrose-recurved, often secund, broadly ovate, abruptly acuminate, often plicate, especially when dry, cordate and broadly decurrent at base; margins serrate to serrulate throughout, plane to erect; costa short and double or none; cells linear to oblong-linear, low-prorulose at upper and sometimes lower ends at back, sometimes smooth, firm-walled, becoming shorter in a few rows across the insertion; alar cells decurrent, subquadrate to oblong, enlarged. Branch leaves smaller than stem leaves, erect-spreading to squarrose, obscurely homomallous to falcate-secund, lanceolate to ovate-lanceolate, gradually acuminate, concave, subplicate, short-decurrent; margins serrate to serrulate above, subentire to serrulate below, plane to recurved; costa short and double or none; cells linear to oblong-linear, conspicuously prorulose at upper and sometimes lower ends at back, firm-walled, becoming shorter in a few rows across the insertion; alar cells subquadrate to short-rectangular. Asexual propagula none. Dioicous or phyllodioicous. Perichaetial leaves erect with spreading apices, oblong to broadly oblong, abruptly long-acuminate, concave; margins serrulate above, serrulate to entire below, plane; costa short and double or none; cells oblong-linear to linear-flexuose, usually smooth, becoming laxly rectangular toward the insertion; alar cells not differentiated. Setae elongate, smooth or rarely roughened, reddish; capsules inclined to horizontal, arcuate, asymmetric, ovoid to broadly cylindric; exothecial cells ± isodiametric, thick-walled on vertical walls, thinner-walled on crosswalls; annulus differentiated; operculum conic, mostly short-rostrate; peristome double, exostome teeth shouldered, bordered, on the front surface cross-striolate below, sometimes with overlying papillae, papillose above, trabeculate at back; endostome with a high basal membrane, segments keeled, perforate, ca. as long as the teeth, cilia in groups of 23, well developed to rudimentary. Spores spherical, finely papillose. Calyptrae cucullate, usually hairy, smooth.

• Discussion

  Ctenidium (Schimp.) Mitt., J. Linn. Soc., Bot. 12: 509. 1869; Hypnum subgen. Ctenidium Schimp., Syn. Musc. Eur. 631. 1860; Stereodon sect. Ctenidium (Schimp.) Mitt., J. Linn. Soc., Bot. 8: 153. 1864. Discussion. Ctenidium has differentiated stem and branch leaves and in many ways is like Mittenothamnium but is distinguished by decurrent leaves, especially those of the stem, with a better alar development. Ctenidium is also characterized by serrate leaves with prorulose cells, and stem leaves that are broadly ovate and abruptly tapered to an acuminate apex. A relationship to Mittenothamnium is unmistakable not only because of gametophytic characters but also because of the unequally thickened exothecial cells. Only a single species is present in the West Indies. The genus was monographed worldwide by Nishimura (1985). More recently Pedano (1996) examined the genus in eastern North America.