Plants in compact to loose cushions or turfs. Stems 0.5–15 cm. Leaves crowded, limbs lanceolate or subulate-lanceolate and concave to subtubulose, erect, spreading, reflexed to flexuose or falcate-secund, little changed when dry, spreading from an oblong-obovate to elliptic sheath; costa consisting of 1–4 layers of abaxial and 1–4 layers of adaxial leucocysts that enclose a central layer of quadrate chlorocysts; inner walls of leucocysts with single pores; external pores often present on the abaxial surfaces of the cell walls of leucocysts in the apical and basal regions of leaves. Specialized asexual reproduction by small, caducous, leaf-like gemmae, and by leaves with rhizoids borne adaxially on exposed chlorocysts at leaf apex. Sexual condition pseudautoicous, with dwarf male plants growing on tufts of tomentum or leaves of female plants. Seta 1(–2). Capsule inclined, asymmetric, plicate when dry, often strumose; operculum long-rostrate; annulus usually absent; peristome teeth 16, divided 1/2 their length, longitudinally pitted-striolate proximally, papillose distally. Calyptra cucullate, often split incompletely to base, which clasp the tip of seta until capsule mature. Spores yellowish or brownish, nearly smooth to minutely papillose.

Distribution

Worldwide except Antarctica in temperate and tropical areas.

Discussion

Species ca. 122 (2 in the flora).

Based on an analysis of ten separate characters of the leucobryoid leaf, J. Burch (1997) suggested that Leucobryum may not be phylogenetically homogeneous, but that possibility remains to be evaluated. The external pores of the leucocysts can be demonstrated by staining with safranin.

Selected References

None.

Lower Taxa

Leucobryum albidum, Leucobryum glaucum

Key

1	Plants in low, compact cushions or turfs; stems less than 1 cm (rarely to 4.5 cm); leaves 2-4(-6) mm, limb subtubulose, erect to wide-spreading, straight, shorter than (rarely equal to) length of sheath.	Leucobryum albidum
1	Plants in tall, compact cushions or turfs; stems mostly 1-12.5 cm (rarely shorter); leaves mostly 3-9 mm, limb concave to subtubulose, erect-spreading, sometimes falcate-secund, 1-2(-3) times length of sheath.	Leucobryum glaucum