Plants small to robust. Stems 2--20 cm. Leaves imbricate, erect to spreading, sometimes appressed, not catenulate, plane or with a single pair of plicae near leaf base. Capsule 2--3 mm.

Capsules mature throughout the year. Rock or soil in seepy, typically open habitats; 0--3500 m; Greenland; Alta., B.C., Man., N.B., Nfld., N.S., N.W.T., Nunavut, Ont., Que., Sask., Yukon; Ala, Alaska, Ariz., Calif., Colo., Fla., Ga., Idaho, Ill., Kans., Maine, Mich., Mo., Mont., Nebr., Nev., N.Mex., N.Y., N.C., Pa., S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., Wyo.; Mexico; c and w Europe; Asia; e and n Africa.

While the breadth of variation in the typical variety is immense, crucial characters include the typically robust habit, the imbricate, laxly erect, straight, falcate or secund leaves. Plants that are subject to prolonged periods of submersion may develop bizarre morphology.