1. Pseudocalliergon angustifolium Hedenas, Lindbergia. 16: 85, fig. 1. 1992. (as augustifolium).
Drepanocladus angustifolius (Hedenas) Hedenas & C. Rosborg
Plants medium-sized, not turgid, with golden gloss when dry. Stems slightly or irregularly pinnate. Stem leaves erectopatent to spreading, falcate, ovate-lanceolate to broadly ovate, gradually narrowed to apex; margins partly or finely denticulate; apex long-acuminate, furrowed or almost tubular; costa single, ending in acumen, <(31-)38-70(-74) µm wide at base, 3-5-stratose>; alar cells rectangular, rarely quadrate, not or slightly inflated, walls thin or incrassate, region transversely triangular; distal laminal cells smooth or often distally prorate abaxially. Perichaetia unknown. Sporophytes unknown.
Mountains, forested and open habitats, rich fens, shallow, wet depressions on lime-rich ground, late snow-bed vegetation; low to high elevations; Greenland; Alta., B.C., N.W.T., Nunavut, Yukon; Alaska, Calif., Colo., Wyo.; n Eurasia; Atlantic Islands (Iceland).
Pseudocalliergon angustifolium been confused with Warnstorfia fluitans, which has similar leaf shape and relatively small or indistinctly delimited alar groups. The differences between P. angustifolium and 2. P. brevifolium are discussed under the latter. Whether the station located by Williams (NY) at Heart Butte in 1897 is located in Montana or North Dakota is unclear.