Gary L. Smith Merrill, Robert R. Ireland Jr.Gary L. Smith Merrill, Robert R. Ireland Jr. from Flora of North America (vol. 27)
Plants large, green to dark green, becoming brown to reddish brown with age. Stems to 6 cm, sometimes matted with whitish rhizoids. Leaves 5-9 × 0.8-1.6 mm, densely imbricate, lingulate to lanceolate, plane to slightly keeled and concave, obliquely transversely undulate, often with rows of teeth on undulations on abaxial surface, the apex attenuate; costa subpercurrent to percurrent, with abaxial teeth along the undulations in distal half; lamellae 4-6, laxly spreading, 2-4(-6) cells high; median leaf cells 24-27(-30) µm wide, rounded to irregularly angled, weakly convex on both surfaces, thick-walled, strongly collenchymatous with trigones, smooth or usually with minute, rounded or striate papillae on abaxial surface. Sexual condition dioicous; male plants as large as females, perigonial bracts small, imbricate, ovate or suborbicular, often more than one perigonial bud in sequence per shoot. Seta 1-3 per perichaetium, 1.5-4 cm, reddish brown. Capsule 4-7 × 0.5-1 mm, usually somewhat curved and inclined, rarely straight and erect; operculum 2-3.5 mm. Spores 12-19 µm.
Capsules mature summer (Jun-Aug). Soil, humus, mostly shaded habitats; often wet banks along streams or sometimes at margins of fens and swamps; low to high elevations; N.B., Nfld. and Labr. (Nfld.), N.S., Ont., P.E.I., Que.; Ark., Del., Ill, Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich. Miss., N.H., N.Y., N.C., Ohio, Pa., Tenn., Va., W.Va., Wis.; e Asia (China, Japan).