This Southern Appalachian taxon has often been combined as a variety with H. arifolia (Michx.) Small, which occurs mostly on the southeastern Coastal Plain. In its strict sense, arifolia is reported from Tenn. (Anderson Co. at BOON, det. L.L. Gaddy) but not from Ky. H. ruthii has smaller calices, more gradually narrowed to the lobes, which are smaller and less spreading (F, Cr, W); lobes are 2-4 mm long (versus 2.5-8 mm) and 2-4 mm wide at base (versus 3-9 mm). Although virtually restricted to Appalachian regions in Ky., there is a coll. labeled as from CHRI (TENN; Gaddy 1987): H. Iltis et al. 23312, 25 Apr 1965, "mixed deciduous upland woods adjacent to camping ground in Pennyrhile State Park..." However, mislabelling is suspected and this record was not mapped in FNA 3; see also Euphorbia mercurialina coll. with similar problem. There is also a student coll. labeled as from ROWA (MDKY) but the locality just "ravine slope... D.B.N.F" [National Forest]; the county is probably erroneous. In morphology, the arifolia complex differs from other Hexastylis species as follows (W): style extension bifid to stigma (versus notched or divided at apex); leaves triangular to ovate-sagittate or subhastate (versus rounded with cordate base), portions of the sides of nearly all leaves straight or concave (versus all convex); leaves mottled with paler areas between the veins (versus unmottled or mottled with paler areas along veins). The chemistry of essential oils (including phenol ethers) in Hexastylis deserves further research (Hayashi et al. 1983; W). D. Stephens (of Whitley City, pers. comm.) has found that the aroma of ruthii is sweet and anise-like, whereas contracta is sassafras-like; they can easily be distinguished by smell alone. D. Barrett (pers. comm.), of Booneville (OWSL), has found that an extract of ruthii is effective in human reproduction.