Bryum acutiforme Limpricht, Tromsø Mus. Aarsh. 21-22: 156. 1901

Plants in dense or open turfs, green, yellow-green, or brown. Stems 1-2 cm, fertile stems comose, innovations evenly foliate. Leaves yellow-green to yellow-brown, somewhat distant, weakly contorted to somewhat imbricate when dry, ovate-lanceolate, concave or sometimes flat, 0.5-2(-3) mm, enlarged toward stem apex; base red near costa, green otherwise, not decurrent; margins plane, limbidium moderately strong, in (1-)2-3 rows; apex acute to acuminate; costa not reaching apex to percurrent, apiculus sometimes present, short, slender; proximal laminal cells long-rectangular, (3-)4-5:1; medial cells somewhat longer, walls incrassate; distal cells 18-25 µm wide, 2-3:1, walls thin to incrassate. Specialized asexual reproduction absent. Sexual condition autoicous. Seta red-brown, 2-4 cm, stout, straight to somewhat flexuose. Capsule red-brown or red, ovate, symmetric, 2-3 mm, mouth yellow to yellow-orange; operculum conic, apiculate; peristome reduced; exostome teeth yellow basally, hyaline distally, lamellae ± straight mid tooth, pores absent along mid line; endostome not adherent to exostome, basal membrane less than 1/2 exostome height, segments with lanceolate to slitlike perforations, cilia absent or rudimentary. Spores with size often variable in same capsule, 28-32 µm, yellow or brown.

Capsules mature Jul-Aug. Moist gravelly to sandy soil, near sea, along streams, around lakes; low to moderate elevations (0-600 m); Greenland; Nfld. and Labr., N.W.T., Nunavut; Alaska; n Eurasia.

Ptychostomum acutiforme is related to P. calophyllum, but differs in its ovate-lanceolate leaves with acuminate apices. The leaves have red to red-brown costae and proximal laminal cells narrower than the more distal cells. The hypophysis is thick and abruptly contracted to the seta.