2. Leucobryum Hampe, Linneae. 13: 42. 1839.
Plants small to large, sometimes robust, 0.5–20 cm high, whitish, grayish or bluish green, in compact or loose cushions. Stems erect, simple or forked; central strand mostly absent, sometimes present. Leaves crowded, appressed, or erect-spreading, sometimes falcate-secund above, linear-lanceolate to lanceolate or subtubulose from oblong-ovate to elliptic sheathing base, acute to mucronate at the apex, often with rhizoids at leaf tips, upper parts of leaves filled mostly by the multi-layered broad costa, laminae confined to the basal parts of leaves with multi-rowed linear cells; alar cells rarely differentiated; margins entire to slightly serrulate at the apex, ± bordered by linear cells up to the leaf apex; costae thick, broad, consisting of 2–8 layers of enlarged leucocysts enclosing a ± median row of small, quadrangular chlorocysts in cross section near leaf base. Dioicous or pseudoautoicous. Male plants dimorphous, sometimes minute, dwarf male plants growing on tomentum or among leaves of female plants; normal male plants as large as female plants. Perichaetial leaves sheathing at the base, abruptly linear-filiform from shoulders. Sporophytes terminal or lateral. Setae erect, elongate, sometimes clustered; capsules more or less cylindrical, asymmetric, inclined to horizontal, rarely erect, ± ribbed, often strumose; stomata lacking; annuli often absent, 1–2 rows of small cells when present; opercula long-rostrate; peristome teeth 16, divided to the middle, lanceolate with a broad base, vertically striolate below and papillose above on inner surface, papillose or smooth on outer surface. Calyptrae cucullate. Spores small to large, finely papillose.
Leucobryum is a group of whitish to grayish looking mosses that are often found growing on acid substrates. The genus is often used to differentiate various types of forest vegetation in lowland coniferous-broadleaf forests in southern China.
There are about 110 species of Leucobryum worldwide, and 19 taxa were recognized in Asia (Yamaguchi 1993). Ten species and one variety are treated from China in this study. We have more or less adopted Yamaguchi's (1993) treatment of Asiatic species. Since he has seen only a few Chinese specimens of Leucobryum, some of the Chinese records may be proved to be synonyms of other species in the future.