Meehan (1898: 18) removed the fragmentary specimen of this taxon from Lewis 43, a sheet of Cleome serrulata (PH-LC 65). Pursh (1813: 441) makes no mention of this taxon being found on the Missouri River, so we suspect Lewis made a mixed collection and this was not noted until Meehan reviewed the specimens. The sample was collected along the Missouri River near Vermillion, in Clay Co., South Dakota (Moulton, 1987a: 468). Meehan reports the plant as Polanisia trachysperma Torr. & A. Gray (Fl. N. Amer. 1: 669. 1840) as does Cutright (1969: 415). (The Lewis & Clark Herbarium Digital Imagery Study Set, ANSP, 2002) On deposit at the Academy of Natural Sciences, Philadelphia Collected by:Meriwether Lewis & William Clark