William Clark made the collection on 28 Jul 1806 when he was apart from Lewis on the Yellowstone River in Rosebud Co., Montana (Moulton, in press). According to Clark's journal, the expedition traveled 73 miles by boat that day from some seven miles downstream from Reservation Creek to the mouth of Graveyard Creek (Moulton, 1993: 243-246). He makes no mention of landfall during the day. Even though the label on the specimen clearly states the plant was gathered along the Yellowstone River, both Coues (1898: 311) and Cutright (1969: 408) suggests that Lewis found the species along the Marias River in Chouteau Co., Montana. In print, Pursh was specific as to location and date: "On the Yellow-stone river. . . . July." We accept the label data as correct. There is no reason to believe that Clark was oblivious to plants. Surely he would not have ignored this curious species. (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 Collection date:07/28/1806