Barbula ambigua Bruch & Schimper, Bryol. Europ. 2: 76, plate 139. 1842

Plants to 2.5 mm. Leaves ligulate to lingulate, 1-2.8 mm, margins entire, undifferentiated at base, apex cucullate to nearly open; costa subpercurrent to percurrent, filaments of 3-6 cells, cells subspheric; cells of leaf base 15-64 µm, medial and distal cells 11-24 µm, occasionally with large solid papillae at leaf tip. Sexual condition dioicous or rhizoautoicous. Seta 5.5-12.5 mm. Capsule urn cylindric, 1.5-3 mm; operculum campanulate, 1-1.4 mm; peristome 600-1200 µm, strongly twisted. Spores 13-24 µm.

Capsules mature Jan-May. Low, desert areas, banks and dry washes, soil and limestone; moderate elevations (400-800 m); Ariz., Calif.; Mexico (Baja California); Europe; Asia (India, Israel, Jordan, Lebanon, Turkey); n Africa; Australia.

In var. ambigua, the cylindric capsules with a long and twisted peristome are distinctive. Forms with short-lingulate leaves may be confused with Aloina hamulus when sterile. Outside North America, var. ambigua may occur as high as 2100 m.