Mapping is provisional. D. maxima, as generally applied, is a variable, high polyploid (2n = 15 x 8 to 26 x 8) that has not been clearly defined or recognized across much of its reported northeastern range, especially in southern sections (F, Cr, K, FNA 7). It is often considered to result from hybridization of diphylla and laciniata (Al-Shehbaz 1988b). A detailed study of plants from eastern N.Y. and southern New England showed general distinction from other species in that region (Sweeney & Price 2001). It may be closest to diphylla but differs as follows: rhizomes not uniform in diameter, distinctly constricted at intervals (versus somewhat uniform); leaves smaller on average, the rhizomal ones 2-7.5 x 1.2-3.7 cm (versus 3.5-8 x 2-6.5 cm) and more broadly shaped; cauline leaves usually alternate, rarely subopposite (versus stricty opposite). However, W indicated more similarity to laciniata, based on other characters. Some colls. mapped here may represent a stable taxon, but others may represent diphylla in a depauperate condition, or may be hybrids of diphylla and heterophylla. Similar uncertainties exist in Tenn., where there may be no verified records (Ch; D. Estes, pers. comm.).