Plants moderate-sized to robust, moderately stiff-stemmed, ± lax, but not compact; green to pale yellow to yellowish brown; capitulum typically strongly convex in open grown forms, but flat and ± 5-radiate in shade forms. Stem pale green to yellowish; superficial cortex of 2 layers of enlarged, thin-walled and well differentiated cells. Stem leaves triangular, triangular-lingulate to lingulate, more than 0.8 mm, appressed, apex obtuse to broadly obtuse, erose to fimbriate; hyaline cells efibrillose and nonseptate. Branches straight and often tapering, often 5-ranked, leaves not much elongate at distal end of branches. Branch fascicles with 2 spreading and 2 pendent branches. Branch stems green, cortex enlarged with conspicuous retort cells. Branch leaves ovate-lanceolate, 1.4--2 mm, straight; slightly undulate and sharply recurved; margins entire; hyaline cells on convex surface with 1 pore per cell at cell apex, concave surface with round wall thinnings in the cell ends and angles; chlorophyllous cells triangular in transverse section and well-enclosed on concave surface. Sexual condition dioicous. Spores 22--28 µm; papillose on both surfaces; proximal laesura more than 0.5 spore radius.

Capsules mature late summer to early fall. Forming carpets in a variety of very poor to poor fen habitats, including sedge fens, pocosins, bay swamps; N.S.; Ala., Ark., Conn., Del., Fla., Ga., Ill., Ind., Ky., La., Maine, Md., Mass., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio, Pa., S.C., Tenn., Tex., Vt., Va., W.Va.; South America.

Sporophytes are uncommon. This species is exclusively New World. It has several strong characters that distinguish it from S. flexuosum, and the opinion of H. A. Crum (1997) that the two species are synonymous is rejected. See discussion of S. flexuosum.