15. Radulina W. R. Buck & B. C. Tan 细锯齿藓属 xi chi xian shu
Acta Bryol. Asiat. 1: 9. 1989 . Trichosteleum sect. Thelidium (C. Müll.) Jaeg., Ber. Thätigk. St. Gallischen Naturwiss. Ges. 1876–77: 419. 1878. Hypnum sect. Sigmatella subsect. Thelidium C. Müll., Linnaea 39: 466. 1875.
Plants medium-sized, slender, often dull, green to golden, in thin mats. Stems creeping, irregularly branched, branches often ascending and falcate-cuspidate; pseudoparaphyllia foliose; axillary hairs with a single, short, brownish basal cell, elongate, hyaline apical cells. Leaves falcate-secund, lanceolate or sometimes ovate-lanceolate, acuminate, concave; margins plane, serrulate above, serrulate to entire below; costae none, occasionally short and double; leaf cells elongate-hexagonal to linear, firm to thick-walled, somewhat pitted, pluripapillose with papillae uni- to biseriate over lumina; alar cells enlarged, inflated, all but outermost thick-walled. Autoicous. Perichaetia inconspicuous; inner perichaetial leaves oblong-lanceolate, abruptly long acuminate. Setae elongate, slender, reddish, papillose above, smooth below; capsules inclined to horizontal, exothecial cells short-quadrate, strongly collenchymatous; opercula obliquely long rostrate; annuli none; peristome double; exostome teeth narrowly furrowed, cross-striolate below, papillose above on outer surface; trabeculate on the inner surface; endostome segments keeled, perforate; basal membrane high, as long as the teeth; cilia single, stout. Calyptrae cucullate, naked, roughened above. Spores medium-sized, finely papillose.