This widespread northeastern species may intergrade with the more southern enslenii (F). R. flagellaris and its close allies differ from the enslenii group as follows (F, Widrlechner 1998): canes generally thicker (ca. 3-6 mm at base versus 2-4 mm), leaves usually firmer, those of primocanes 3- or 5-foliate (versus just 3), the leaflets usually ovate (versus ovate to elliptic), more abruptly acuminate and rounded at base (versus cuneate); flowers usually in groups of 2-9 (versus solitary or sometimes 2-3). Ladd & Thomas (2015) indicated that there is much variation in pubescence. Mapped records here include the closely related taxa, R. fecundus Bailey, R. vixalacer Bailey, R. felix Bailey, R. nefrens Bailey, R. celer Bailey and perhaps R. steelei Bailey. See also notes under R. aboriginum. Some additional colls. from these same mapped counties are referable to R. meracus Bailey (CAMP, CARL, LEWI) or R. mundus Bailey (BULL, MCRE, POWE). The latter two taxa are more hairy than typical R. flagellaris and may be considered transitions to R. roribacus. Some of these many taxa may be worth recognizing, and will be examined further when M. Medley's colls. are processed at WKY.