Further investigation of these plants is needed. P. torreyi is reported to have a relatively small range from mid-Atlantic states, especially on or near the Piedmont, to the central Mississippi Valley, and it largely absent or poorly known between these two concentrations (K). In Ky. the species appears largely restricted to remnants of dry native grassland of the Big Barrens region or nearby. P. torreyi reportedly includes tetraploids and hexaploids (2n = 78/80 and 120; Chambers 1993). It differs from verticillatum (and pilosum) in its longer calyx teeth (ca. 1-1.5 mm versus 0.5-1 mm), and glabrous upper leaf surfaces (versus canescent, at least on bracts); also leaves are generally narrower than verticillatum or pilosum (mostly 8-12mm versus 10-15 mm). Superficially, it appears transitional to tenuifolium and hybrid origin is suggested. See also notes under virginianum, which may be difficult or impossible to distinguish in some cases. The spelling "torrei" can be considered an orthographic variant (W).