1. Tomentypnum falcifolium (Renauld ex Nichols) Tuomikoski, Ann. Bot. Fenn. 4: 435. 1967.
Camptothecium nitens var. falcifolium Renauld ex Nichols, Rhodora 15: 12. 1913; Homalothecium nitens var. falcifolium (Renauld ex Nichols) Wijk & Margadant; Tomentypnum nitens var. falcifolium (Renauld ex Nichols) Podpěra
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.
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.
SELECTED REFERENCE Vitt, D. H. and C. D. Hamilton. 1975. Taxonomic status of Tomenthypnum falcifolium. Bryologist 78: 168-177.