This is a highly variable eastern species, as currently defined. Potential segregates need further study, but may be intergradient; 2n = 90 in general (FNA 2; W). See notes under var. dissectum. Some plants of dissectum in e. Ky. and Tenn. have relatively long, linear (parallel-sided), pinnules (especially lower ones); these have "somewhat blunt-tipped segments with a more or less whitish gray central line above the veins" (FNA 2). These plants were provisionally named B. johnsonii or B. parallelum by W.H. Wagner, but have not been formally described (Johnson 1960). They are known from ADAI, BOYD, FLOY, JOHN (with provisional type), PIKE and ROWA (M).