Monographs Details: Thuidium
Authority: Sharp, Aaron J., et al. 1994. The Moss Flora of Mexico. Part Two: Orthotrichales to Polytrichales. Mem. New York Bot. Gard. 69 (2)
Description:Genus Description - Fairly robust plants in dull, green, yellowish, or brownish, loose mats. Stems creeping to ascending, often 1-3-pinnate and often frondose; paraphyllia abundant, papillose, branched-polymorphous. Stem and branch leaves differentiated. Stem leaves ovate or subcordate, acuminate, narrowed to the base and somewhat decurrent, generally ± biphcate; margins ± revolute below, not or somewhat toothed above; costa ending below the apex or, rarely, excurrent; cells mostly uniform, rounded- to oblong-hexagonal, firm- or thick-walled, unipapillose or, less often, pluripapillose at back. Leaves of primary branches often rather similar to stem leaves; leaves of secondary and tertiary branches much smaller than the other leaves, concave, with erect margins, mostly ovate, acute or sometimes obtuse or rounded, usually ending in a tmncate cell with more than 1 papilla, and costa shorter and weaker. Perichaetial leaves elongate, erect, pale, lanceolate or ovate-lanceolate, long-acuminate, sometimes ciliate at the margins; costa ending in the acumen or subpercurrent; cells elongate, smooth or somewhat papillose. Setae elongate, smooth; capsules inclined to horizontal and ± curved, oblong-cylindric, smooth; annulus of 2-3(-4) irregular rows of cells; operculum conic or convex-conic, often obliquely rostrate; exostome teeth yellow or yellow-brown; cilia of endostome ± nodulose, in groups of 2 to 4 (rarely rudimentary or lacking). Calyptrae naked.
Regularly pinnate branching, abundant paraphyllia, papillose leaf cells, and obvious differentiation of stem and branch leaves are important features of the genus. It differs from Cyrto-hypnum in its larger size, dioicous inflorescences, leaf cells papillose only at back, and smooth setae.