Pottia fosbergii E. B. Bartram, Bryologist 33: 18. 1930; Phascum fosbergii (E. B. Bartram) J. Guerra

Stem leaves mucronate to short-awned. Capsule cleistocarpous, peristome rarely differentiated internally, operculum absent or occasionally weakly differentiated. Spores both tuberculate and papillose, occasionally nearly smooth.

Capsules mature in early spring (Mar). Soil; low to moderate elevations; Calif.; Mexico (Baja California).

Variety fosbergii has elliptical capsules that lack both a differentiated operculum and a peristome (except California: Ikenberry, CANM, which has a weakly differentiated operculum and rudimentary peristome teeth). This variety apparently has spores that are both tuberculate and papillose (also true in the type), occasionally nearly smooth. If the spores are unreduced (though there is no evidence they are), then hybridization would be implicated. R. M. Ros et al. (1994) have described from Spain a putative hybrid between Microbryum starckeanum and Tortula protobryoides (as Pottia bryoides), which is evidently much the same as the var. fosbergii.