The specimen is sterile but the identification is sound (see Meehan, 1898: 30). The fragmentary material was annotated "A Shrub within the Rocky mountains / found in moist grounds near branches of riverlets" and dated 7 Jul 1806. On that day Lewis was along the Blackfoot River in Lewis and Clark Co., Montana (Moulton, 1993: 95-96), whereas Clark was in Big Hole Valley in Beaverhead Co. (Moulton, 1993: 164-166). Either could have found the plant; neither explorer mentions it. Cutright (1969: 410) lists the plant as Xylosteum involucratum Richardson (in J. Franklin, Narr. Journey Polar Sea, Bot. App.: 733. 1823). (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:07/07/1806