Mapping here is provisional. This species occurs mostly on acidic soils of the Atlantic and Gulf Coastal Plains (K, W). It was reported from Ky. in FNA 22, but details are not available. Colls. mapped here may all be transitional to interior or tenuis; they are mostly from artificial lake shores, strip-mines and construction sites. J. dichotomus is close to interior, and has probably been much confused (e.g. Ch). It differs in its usually deeper brown capsules (with "reddish", "castaneous" or "shining mahogany" tint), leaves almost terete to slightly channeled (versus flat), and sheaths deeper brownish or the inner ones often purplish (F, Cr, FNA 22, Y). Inflorescences may be generally more congested; and primary bracts are sometimes relatively short (as in secundus), but these characters are inconsistently reported. Included here are plants of Ohio and Ky. that were initially described as J. dichotomus var. platyphyllus Wieg. That taxon has been considered a distinct species of eastern regions, inland to the Appalachian Plateaus (F, Braun 1967). It tends to have more flattened leaves, longer auricles, paler sheaths and paler capsules, suggesting a transition to tenuis.