4. Bartramia Hedwig, Sp. Musc. Frond. 164. 1801. • [For John Bartram, 1699-1777, Pennsylvania botanist, horticulturist, and explorer].
Plants in lax to dense tufts, dull green to glaucous, sometimes yellowish or yellowish brown distally. Stems 0.5-15 cm, erect, 2-fid, lacking subfloral whorl of branches; rounded in cross section, hyalodermis present, indistinct to distinct, epidermis not prorulose; radiculose proximally, rhizoids papillose. Leaves not in distinct rows or rarely in 5 rows, erect-appressed to spreading or circinate, sometimes flexuose when dry, spreading when moist, narrowly lanceolate to linear, 2- or 3-stratose at margins or throughout; base ± sheathing; margins plane or revolute, entire proximally, serrate to serrulate distally, teeth single or paired; apex acuminate or subulate; costa subpercurrent to excurrent, abaxial surface prominent, rough, or sometimes obscure in distal limb; basal laminal cells elongate to rectangular or linear; distal cells subquadrate to oblong-linear, prorulose on both surfaces, walls firm. Specialized asexual reproduction absent. Sexual condition dioicous, autoicous, or synoicous; perigonia gemmiform; perichaetial leaves little differentiated from stem leaves (differentiated in B. ithyphylla). Seta single (often 2 or 3 per perichaetium in B. halleriana), elongate or rarely short, straight or sometimes curved. Capsule inclined or sometimes erect, subglobose, globose, ovoid, or pyriform, furrowed when dry, mouth oblique; annulus not distinct; operculum convex to conic; peristome double, single, or absent; exostome teeth reddish brown, lanceolate, smooth or papillose, apically free; endostome pale yellow, sometimes absent, segments keeled, cilia rudimentary or absent. Spores reniform to subspheric, coarsely to warty papillose.
Species ca. 90 (7 in the flora): nearly worldwide, except Antarctica; especially diverse in montane tropics.
Bartramia is generally recognized by its linear-lanceolate leaves and sheathing base with a distal lamina that is 2- or 3-stratose at the margins or throughout. The plants may be soft or rigid; the stem cortical cells have somewhat firm walls. The leaves are not plicate; the basal laminal cells are pale and smooth with walls thin or rarely thick toward the costa. The perichaetial leaves are usually less prorulose with more lax areolation; the exostome teeth are sometimes cleft distally and lack intermediate abaxial thickenings. Bartramia stricta lacks a sheathing leaf base but otherwise is in accord with the generic concept.