1d. Polytrichastrum alpinum (Hedwig) G. L. Smith var. fragile (Bryhn) D. G. Long, Meddel. Grønland, Biosci. 17: 30. 1985.
Polytrichum fragile Bryhn, Bryoph. Itin. Pol. Norv., 122, plate 122, fig. 3. 1906; Pogonatum alpinum var. fragile (Bryhn) H. A. Crum; Polytrichum alpinum var. fragile (Bryhn) Nyholm
Stems 1-2 cm, in compact tufts. Leaves fragile, constricted at the junction of sheath and blade, the blade caducous; marginal lamina entire, rarely distantly serrulate. Capsule ovoid or subglobose.
Growing where subject to periodic inundation, wet meadows, springs and lake margins, occasional in open tundra, beach ridges and roadside banks, low elevations; Greenland; N.W.T., Nunavut; Alaska; Europe (n Scandinavia); Asia (Russia in Siberia).
Variety fragile is a distinctive taxon of the high Arctic with regularly caducous leaves, in North America common only in arctic Alaska on the coastal plain to 100(-800) m, with scattered records throughout arctic Canada (D. G. Long 1985). In Nunavut, it is known from Baffin Island, Ellesmere Island, and Melville Island.