8. Desmatodon Brid., Muscol. Recent. Suppl. 4:86. 1819[1818].
链齿藓属
Plants small, green, yellowish green to yellow, in low loose tufts. Stems short, usually simple, rarely branched; central strand present, rarely absent. Leaves usually flexuous or curved-contorted when dry, erect-spreading when moist, often concave or keeled-concave, broadly ovate, narrowly obovate or oblong- to ovate-lanceolate, acute, obtusely pointed or apiculate to hair-pointed at the apex; margins mostly entire, revolute below, plane, serrulate above, sometimes borders differentiated by linear cells near leaf bases, but by short, incrassate cells in the upper margins; costa percurrent to excurrent, or ending in a hairy awn, smooth or papillose; in cross section dorsal stereid band present; upper leaf cells orderly arranged, quadrate to hexagonal or oblong-hexagonal, thin-walled, with multiple C-shaped papillae, or occasionally smooth; basal cells larger, lax, irregularly rectangular, smooth, hyaline. Autoicous. Perichaetial leaves not much differentiated from stem leaves. Setae elongate, straight, twisted or cygneous, smooth; capsules usually erect, symmetric, ovoid- to oblong-cylindrical; annuli developed, deciduous or persistent; peristome teeth nearly erect, occasionally twisted once, short and flat, rather broad, lanceolate, with a low basal membrane, usually divided 2–3 times, densely papillose, rarely peristome rudimentary or absent; opercula conic, obliquely short- to long-rostrate. Calyptrae cucullate, smooth. Spores rather large, spherical, yellow or reddish brown, mostly coarsely papillose.
Desmatodon is similar to Pottia and Tortula in many aspects. It is considered to be indistinct from Tortula by Zander (1993). However, we agree with P.-C. Chen (1941) that Desmatodon can be separated from the species of Tortula by the peristome structures. Desmatodon has a peristime arising from a low basal membrane, with divisions rather broad in pairs, nearly erect, and free. In contrast, Tortula has a peristome wound in spiral on a high basal membrane, with divisions more nearly terete and equally spaced. The leaves of Desmatodon are softer and not crisped when dry, while those of Tortula are more or less rigid and usually contorted when dry. Furthermore, in Desmatodon, the leaf cells are laxer and more translucent, with papillae grouped in a central areas; while in Tortula, the leaf cells are firm and less translucent, with papillae arranged around their margins. In this treatment, we have followed Chen’s study and recognized 10 species of Desmatodon from China.
