Weissia acuta Hedwig, Sp. Musc. Frond., 71. 1801

Plants often blackish or dark brown, sometimes olive green. Leaves secund to often deciduous, lanceolate-subulate, obtuse, costae filling subula; margins denticulate at apex, entire below, leaf cells (1-)3:1, quadrate to rectangular-elliptic; perichaetial leaves abruptly subulate. Seta 3-13 mm, flexuose. Capsule ovate to narrowly pyriform, peristome of 16, lanceolate teeth; columella not developed. Spores 13-20 µm.

Moist or dripping acidic rock faces; most common in montane/alpine habitats; low to high elevations (0-3000 m); Greenland; Alta., B.C., N.B., Nfld. and Labr. (Nfld.), N.W.T., N.S., Nunavut, Ont., Que., Yukon; Alaska, Calif., Colo., Mich., Minn., Mont., N.H., N.Y., N.C., Oreg., Penn., Tenn., Vt., Wash., Wyo.; Central America (Guatemala); Europe; Asia; Africa; Atlantic Islands (Iceland).

Blindia acuta forms soft blackish mats on acidic rocks in moist arctic, alpine, and montane habitats. The well-developed alar cells, smooth leaf cells, subulate leaves, and short-ovate, smooth capsules with well-developed, smooth peristome teeth are distinguishing features. Seligeria species are smaller and occur on calcareous rocks.