Plants small, in lax to dense tufts, bright green, rufous proximally. Stems 1-3 cm, lax, simple or 2-fid, tomentose proximally. Leaves laxly erect to erect, sometimes secund when dry, erect-spreading when moist, narrowly triangular- lanceolate, 1-2.5 mm; margins narrowly revolute, serrulate nearly throughout, teeth single or paired; apex acuminate; costa excurrent, abaxial surface weakly papillose; laminal cells , prorulose, ; basal cells rectangular, shorter, broader than distal, to 45 × 12 µm; distal cells linear, 30-65 × 5-7µm. Specialized asexual reproduction absent. Sexual condition autoicous; perigonia gemmiform. Seta 1.5-3.5 cm, straight or flexuose. Capsule 1.8-2 mm. Spores reniform, 26-33 µm.
Philonotis longiseta (Michx.) Britt., Bryologist 14: 44. 1911.
Bartramia longiseta Michx., Fl. Bor.-Amer. 2: 301. 1803. Protologue: Carolina and Virginia. In Carolina, ex herbario D. Bosc, et in Virginia ex D. Beauvois.
Philonotis graminicola C. Müll., Linnaea 38: 632. 1874. Protologue: Mexico. Orizaba? Satorius in Hb. C. Mohr. Ex Hb. Hmp. a Freder. Müller in monte Orizaba lectam habeo.
Plants small to medium-sized, in loose, yellowish‑green or green tufts, to 15 mm high. Stems red; rhizoids at base, reddish brown, smooth to lightly roughened. Leaves 1–2.5 mm long, erect to erect-spreading when dry or erect-spreading when wet, straight or secund, lanceolate to triangular-lanceolate; apices acuminate; margins narrowly revolute, singly or doubly serrate; costa long-excurrent; cells papillose, papillae at upper cell ends, upper cells rectangular, firm‑walled, 25–47 x 6–8 μm, basal cells rectangular, to 50 x 12 μm, alar cells short-rectangular or with 2-3 quadrate cells at extreme base. Autoicous. Perigonia gemmiform, axillary, below the perichaetia. Setae 10–33 mm long, red. Capsules 2–3 mm long, brown, ovoid to subglobose, inclined to pendent, abruptly constricted at neck; exothecial cells thick-walled; opercula 0.5 mm long, conic‑mammillate; peristome double, exostome teeth red, outer surface densely and thickly papillose above, finely and evenly papillose below, trabeculae thin, inner surface smooth, trabeculae thick, endostome yellow, evenly papillose throughout, basal membrane short, each segment split along the median line and each half diverging toward the cilia, cilia 1–3, short, stout. Spores reniform, 20–27 μm, papillose.