Plants small to large, in tufts, mats, or sods, light to dark green or yellowish, sometimes reddish or glaucous, reddish brown proximally. Stems 1-16(-20) cm, erect, simple, irregularly branched, or with a subfloral whorl of innovations, tomentose proximally. Leaves (with distalmost rarely spiraled around stem), stiffly erect to erect or erect-spreading, less commonly catenulate, erect to erect-spreading when dry, erect to spreading or occasionally secund when moist, lanceolate to broadly ovate-lanceolate or ovate-subulate, 0.6-3 mm; margins revolute, serrulate throughout, teeth paired, appearing 2-fid due to their apposing position from contiguous cells, sometimes margins plane, teeth unpaired; apex gradually to abruptly acute to acuminate, sometimes obtuse; costa short- to long-excurrent (often subpercurrent in obtuse leaves), <320 µm wide at base>, distal abaxial surface smooth or weakly prorulose; laminal cells prorulose at proximal ends on abaxial side and at proximal and distal ends on adaxial side; basal cells rectangular to oblong-hexagonal, 15-30 × 5-8 µm; ; distal cells linear to oblong-linear, 15-40 × 3-5 µm. Specialized asexual reproduction absent. Sexual condition dioicous; perigonia discoid. Seta 2-5(-7) cm, straight. Capsule 1-3.5 mm. Spores ovoid to reniform, 18-30 µm.
6. Philonotis fontana (Hedw.) Brid. 泽藓 ze xian Bryol. Univ. 2: 18. 1827. Bartramia fontana (Hedw.) Turn., Muscol. Hibern. Spic. 107. 1804. Mnium fontanum Hedw., Sp. Musc. Frond. 195. 1801. Type: Europe. Philonotis lutea Mitt. J. Proc. Linn. Soc., Bot., Suppl. 1: 63. 1859. Plants medium-sized to large, yellowish green, glossy, in dense tufts. Stems erect, 2–10 cm high, usually branched, densely tomentose below, rhizoids smooth. Leaves dense, erect-spreading, more or less secund, ca. 2.0–2.5 mm long, cordate or broadly ovate at base, distinctly plicate, gradually acuminate at apex; margins recurved, serrulate; costae percurrent or shortly excurrent; leaf cells with papillae at upper cell ends above, at lower ends below; upper cells elongate-rhomboidal to sublinear; lower cells rectangular to subquadrate. Dioicous. Setae 1.5–3.5 cm long; capsules ovoid, 2.5–3.0 mm × 1.7–2.0 mm, suberect to inclined, furrowed when dry. Spores not seen.
Philonotis fontana (Hedw.) Brid., Bryol. Univ. 2: 18. 1827.
Mnium fontanum Hedw., Sp. Musc. Frond. 195. 1801. Bartramia fontana (Hedw.) Turn., Muscol. Hibern. Spic. 107. 1804. Protologue: Locis paludosis apertis spongiosis. Maio et Junio sporangia maturat. Perenne.
Plants medium to large-sized, in dense yellowish green or green, glossy tufts, to 80 mm high. Stems red, densely tomentose below; rhizoids reddish brown, smooth. Leaves 1.4–2.1 mm long, moderately spaced, erect to erect-spreading when dry, erect-spreading when wet, straight or secund, ovate-lanceolate; apices slenderly long-acuminate; margins narrowly revolute, jugate, singly or doubly serrate; costa long-excurrent; cells papillose, papillae at lower cell ends on median and basal cells, papillae at upper cell ends on apical cells, upper cells sublinear, rectangular or oblong, firm‑walled, 12–38 x 5–7 μm, basal cells rectangular to subquadrate, 12–30 x 5–8 μm, alar cells quadrate in 2–3 rows. Microphyllous branches sometimes present in leaf axils. Dioicous. Perigonia discoid. Setae straight, 2–4 cm long. Capsules inclined, 2–4 mm long, ovoid to subglobose, furrowed when dry, striate when wet; exothecial cells short, thick-walled; opercula conic, 0.3–0.5 mm long; peristome double, exostome teeth narrowly triangular, to 500 μm, outer surface finely papillose below, coarsely papillose near tips, trabeculae thin, inner surface smooth, trabeculae thick, endostome nearly as long as the exostome, yellowish, finely papillose granulose below, segments split along the median line and each half diverging toward the cilia, cilia 3–4, well-developed. Spores ovoid or subreniform, 20–30 μm, coarsely papillose. [Sporophytes and gametangia unknown in Central America, description based on North American material.]