[Camptothecium nitens var. falcifolium Ren. ex Nichols, moreHomalothecium nitens var. falcifolium (Renauld ex Nichols) Wijk & Margad., Tomenthypnum falcifolium , Tomenthypnum nitens var. falcifolium , Tomentypnum nitens var. falcifolium Ren. ex Nichols]
Stems: with rhizoids restricted to stem leaf proximal costa surface. Leaves: falcate-secund, often twisted distally, gradually narrowed to apex, widest just beyond base, slightly narrowed to insertion; apex slender-acuminate. Seta: reddish, darker proximally, lighter distally, 2.5–4.5 cm, slightly twisted when dry, straight to somewhat flexuose. Calyptra: naked. Phenology: Capsules mature early-mid summer.
Acidic, oligotrophic environments, with Sphagnum species on hummocks and turfs. low to high elevations. Greenland, Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Nunavut, Ont., Que., Sask., Conn., Maine, Mich., Minn., N.Y., Asia (China, Siberia).
The shape of the leaf base in Tomentypnum falcifolium is best observed while the leaves remain attached to the stem. The species is widespread but more sporadic than T. nitens, occurring across the boreal and subarctic areas of Canada, extending south into the northeastern United States.