Plants slender, in yellowish or bright green tufts, brown-tomentose proximally. Stems erect, simple or forked, 1--6 cm. Leaves 1--2.3 mm, erect-spreading when dry, somewhat divergent when moist, occasionally spiraled, triangular-lanceolate, acuminate, keeled; margins plane or sometimes narrowly revolute, serrulate nearly to base, teeth single; costa percurrent to long-excurrent; distal laminal cells linear oblong, 20--30 × 4--8 µm, prorulose , prorulae rounded, near the distal ends of cells or occasionally at both ends, basal cells oblong, 18-45 × 6--15 µm. Specialized asexual reproduction by propagulae occasionally borne in leaf axils. Sexual condition dioicous; perigonia discoid. Seta 1.5--4 cm. Capsule 1--2.5 mm. Spores 20--30 µm, papillose.

Capsules mature Mar.--Sept. Rocks and soil in wet places, roadsides, springs; 35--3000 m; Alta, B.C., Man., N.S., Que.; Ala., Ariz., Ark., Colo., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Mich., Minn., Miss., Mo., Nebr., N.C., N.H., N. Mex., N.Y., Ohio, Okla., Oreg., Pa., Tenn., Tex., Utah, Va., Vt., W. Va., Wis., Wyo.; Mexico; Central America; South America (Colombia); Europe; Asia; n Africa; Atlantic Islands (Macaronesia).

Philonotis marchica is recognized by the usually plane, singly serrulate leaf margins and the laminal cells bearing rounded prorulae near the distal ends. Philonotis capillaris, a species mainly of Pacific coastal habitats, shares with P. marchica the singly serrulated leaf margin; however, P. capillaris, in contrast to P. marchica, has a more or less decumbent, flaccid habit, more distant, widespread leaves, shorter and broader distal laminal cells and obscure prorulae in the basal half of the leaf.