Phascum flexuosum Schwägrichen, Sp. Musc. Frond. Suppl. 2(1,1): 101. 1823; Bruchia brevicollis Lesquereux & James; B. donnellii Austin; B. sullivantii Austin

Distal leaves long-subulate beyond an ovate, obovate, or elliptic base, 0.9-3.1 mm, leaf base usually strongly differentiated in shape; distal laminal cells short- to long-rectangular. Sexual condition paroicous. Seta 0.5-3 mm. Capsule neck short, obovate. Spores spinose or occasionally spinose-reticulate. Calyptra smooth.

Capsules mature spring-summer. Most soil, fields, among grasses; low to moderate elevations; Ont., Que.; Ala., Ark., Calif., Conn., Del., D.C., Fla., Ga., Ill., Ind., Kans., Ky., La., Maine, Md., Mass., Minn., Mo., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Va., W.Va., Wis.; Europe.

As discussed in detail by A. E. Rushing (1986), Bruchia flexuosa is the most widely distributed and most morphologically variable species of the genus.