The sheet at The Academy of Natural Sciences has two collections and we designate the left-hand specimen with flowers as the lectotype. In his original description, Pursh gives the location as "On the waters of the Clarck's river" but then distinguishes the species on the basis of floral features. Flowers are critical to the technical identification of the typical expression of this species should one wish to distinguish infraspecific entities (e.g., see Hu in J. Arnold Arbor. 36: 52-109. 1955). The lectotype was collected along the Clearwater River in Nez Perce Co., Idaho, on 6 May 1806. During the day, the expedition moved from the mouth of the Potlatch River to just downstream of Pine Creek. No mention is made of the plant. Moulton (1993: 12-13) suggests that Lewis's references to "sevenbark" on 10 Jun (p. 10) is to this species, but states that "Lewis had pressed a specimen of it four days earlier" (but see Physocarpus capitatus, No. 143 below). The specimen was pressed on 6 May, not 6 Jun. The paratype was gathered on 4 Jul 1806 when Lewis was along the banks of the Clark Fork near present-day Missoula, Missoula Co., Montana, during the morning hours of that day. Later in the day his party turned up the Blackfoot. No mention is made of the plant (Moulton, 1993: 87-90; see fig. 4, p. 105). (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