Gymnostomum pyriforme Hedwig, Sp. Musc. Frond., 38. 1801; Physcomitrium californicum E. Britton; P. drummondii E. Britton; P. kellermanii E. Britton; P. megalocarpum Kindberg; P. pygmaeum James; P. turbinatum (Michaux) E. Britton

Plants light green or yellowish green. Stems 0.2-15(-25) cm. Leaves obovate to ovate-lanceolate, distal leaves 2-5 mm; margins toothed, sometimes nearly smooth distally; percurrent to rarely short-excurrent. Specialized asexual reproduction absent. Seta (1-)6-15(-30) mm. Capsule exserted, 1-3 mm, globose-pyriform when young, highly variable in shape when old, urceolate to pyriform; neck short, distinct; exothecial cells irregular hexagonal; suboral cells consisting of 5-17 rows of rectangular cells. Spores (24-)46-60(-90) µm, papillose.

Capsules mature late fall-spring. Wet soil in disturbed places; low to high elevations; Alta., B.C., Man., N.B., N.S., Ont., Que., Sask.; Ala., Ark., Calif., Colo., Conn., Del., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Nebr., N.H., N.J., N.Y., N.C., N.Dak., Ohio, Oreg., Pa., S.C., S.Dak., Utah, Vt., Wash., W.Va., Wis., Wyo.; Mexico; Eurasia; Africa; Australia.

Physcomitrium pyriforme is morphologically variable and widespread across the continent. Plant size, leaf characters, and shape of the capsule vary from place to place and often within populations.