Bryol. Univ. 1: 399. 1826. -- Dicranum virens Hedw., Spec. Musc.
142. 1826. -- Cynodontium vairens (Hedw.) Schimp., Coroll. Bryol. Eur. 12. 1856.
Plants in dense, golden green to yellow green cushions, to 40 mm high. Leaves erect spreading to erect when moist, often with flexuose apices, crispate when dry, distally keeled, not at all fragile. Larger stem leaves to 4 mm long, with an ovate loosely sheathing base constituting about 1/3–1/5 of leaf length, gradually contracted into a flexuose limb. Median cells of leaf limb in regular rows, 6–8 µm wide, quadrate to short rectangular, 1–1.5:1, smooth with rounded lumens, only slightly reduced in size from costa to margin. Alar region somewhat auriculate, only gradually demarcated with its cells inflated and thin walled, quadrate to short rectangular, 1–1.5: 1, to 20 µm wide. Basal juxtacostal cells similar to alarf cells but proportionately longer, 2–3: 1. Costa well defined from base to apex, strongly convex and smooth on abaxial surface, excurrent. Costa cross-section with a single layer of guide cells, with two strong stereid bands, and with well developed ab- and adaxial epidermises. Margin recurved to above the middle, bistratose at least in part, remotely serrulate distally to entire almost throughout. Rhizoids mostly quite dense, red brown and smooth, to 20 µm wide at insertion, monopodially densely branched, inserted on isodiametric nematogons arranged in decurrent streaks from the basal angles of the leaves. Stem cross-section with a strong central strand, with large and pachydermous inner cortical cells, and with up to 5 layers of abruptly differentiated, small, pachydermous and brown outer cortical cells.
Autoicous with male and female plants very similar. Perichaetial leaves similar to adjacent vegetative leaves. Monosetous with the seta yellow- to red-brown,to 20 mm long, straight and smooth. Urn inclined to horizontal, strongly arcuate, to 2 mm long, about 2: 1, strongly strumose, smooth to wrinkled but not sulcate. Operculum rostrate, to 1/2 as long as urn, with isodiametric cells on flaring portion of base in up to about 10 rows, abruptly differentiated into elongate cells on rostrum. Exothecial cells irregular in size and shape, not in regular rows, to 30 µm broad, 0.5–2: 1. Exothecial cells near mouth of capsule isodiametric with rounded lumens, abruptly reduced in up to 4 rows. Stomata present only at base of urn. Annulus deciduous, in about two rows of thin walled, quadrate cells. Peristome red brown, inserted near mouth of capsule, erect when dry, lanceolate, to 500 µm long, bifid to about the middle but with irregular perforations even near the base. Dorsal face of peristome with vertical to oblique striations and with papillosity of apex sparse to non-existent. Ventral face of peristome papillose to base. Spores to 22 µm in diameter, finely papillose.