This western species is a rhizomatous, diploid (2n = 16) relative of the alien sylvestris. R. sinuata has distinctive "small, vesicular, hemispherical trichomes that may be collapsed and scale-like in dried specimens" (Cr). It has been recorded from HARD (MM for WKY) and HICK (BT), but colls. have not been relocated and checked. The few records from Tenn. also need confirmation (W; reported Rutherford Co. coll. at MTSU) However, there are verified records from several coumties in adjacent s. Ill. and se. Mo. (PL, Y).