The degree of distinction in this widespread North American taxon from engelmannii and ovata needs further seessment; 2n = 10 in all three taxa (see notes under those names). Some colls. from GARR, LAUR and POWE (EKY) are referable to the depauperate form previously known as var. jejuna Fern. E. lanceolata Fern. is another closely related species that may be expected, at least as intermediate plants (FNA 23). Although that species occurs mostly in south-central states west of the Mississippi Rv., it has been recently reported from Tenn., in wet open woods on Fort Campbell (Ch; D. Estes, pers. comm.). It has more lanceolate spikelets, relatively short perianth bristles, and strictly bifid flowers (versus trifid or mixed); see FNA 23, W, Ladd & Thomas (2015).