Though initially described from Japan, this taxon is widely scattered across northeastern states and adjacent Canada, where it probably originated (Schuyler 1967; FNA 23, W). S. hattorianus is a cryptic relative of atrovirens that has been combined by some authors (e.g. Cr). It has less septate-nodulose lower blades and sheaths; spikelets tend to be more broadly ovate, with more blackish (versus brownish) scales; achenes are usually shorter (0.7-1.1 mm versus 1-1.3 mm), with bristles somewhat intermediate between atrovirens and georgianus; 2n = 56. A coll. from CLAR (GH) was determined as this species by G.C. Tucker and others: M.R. Beckett #643, 6 Jul 1955, margin of stream, Elkin Station Road. It has also been found nearby in Adams and Sandusky Counties, Ohio (colls. of A. Cusick at DOV).