Authors: Richard E. Andrus

Plants slender and weak-stemmed, moderate-sized, flaccid and plumose when submerged and stiffer and more compact when emergent; green to yellow, usually not tinged with brown or red; capitulum well defined, flat in submersed forms and more rounded in emergent forms. Stems green; superficial cortex of 2--3 layers of enlarged thin-walled cells. Stem leaves long triangular-ovate, 1--2 mm; usually appressed; apex acute to apiculate, hyaline cells only rarely septate or aporose$ but often fibrillose in apical region. Branches unranked, straight to slightly curved, leaves somewhat elongated at distal end. Branch fascicles with 2 spreading and 2--3 pendent branches. Branch stems green, cortex enlarged with conspicuous retort cells. Branch leaves 1.5--2.7 mm, ovate-lanceolate to lanceolate, 1.5--2.7 mm; straight to falcate toward branch tips; when dry often undulate and lightly recurved, margins entire to rarely weakly toothed along the margins in flaccid aquatic forms, hyaline cells on convex surface with 0--1 small round pores at apex, on concave surface with faint round wall thinnings in cell apices and angles; chlorophyllous cells triangular to trapezoidal in transverse section, broadly exposed on the convex surface and exposed slightly to broadly on the concave surface. Sexual condition dioicous. Spores 30--43 µm; the superficial surface coarsely papillose to papillose reticulate.

Widespread, forming wet carpets in weakly minerotrophic mires; Nfld., N.S.; Ala., Conn., Del., Fla., Ind., Maine, Mass., Mich., Minn., N.H., N.J., N.Y., N.C., Ohio, Pa., S.C., Tenn., Vt., Va.; Europe.

Sporophytes are uncommon. See discussion of S. cuspidatum for taxonomic distinctions. Spore characters from K. I. Flatberg (1988).