Publication: Proc. Amer. Acad. Arts. 34: 502. 1899.
selected vouchers: WTU
Notes: FNA23: "Scirpus atrocinctus differs from S. pedicellatus by having more intense pigmentation in its inflorescence, both in the scales and the bases of the involucral bracts. Scales of S. atrocinctus are usually distinctly blackened, at least distally, and those of S. pedicellatus show either no black pigment at all or indistinct blackening beside the distal part of the midrib. Brown streaking throughout the scale is usually prominent in both species. The bases of the involucral bracts are almost always solid black in S. atrocinctus and reddish brown, brownish, or merely tinged or bordered with black in S. pedicellatus. The scales of S. pedicellatus also differ from those of S. atrocinctus in usually having a short mucro. All of these characteristics are variable. The two species are usually quite distinct when they grow close together, and they are not known to hybridize with each other (although each species hybridizes with S. cyperinus). It is often difficult to identify isolated herbarium specimens with confidence.
Scirpus atrocinctus often hybridizes with S. cyperinus and forms hybrid swarms. The type of S. pedicellatus forma viviparus F. G. Bernard appears to be S. atrocinctus × cyperinus."