Of Kans. to Ark. and Tex., occurs in Mo. apparently as an introduction. It has the stellate hairs of the lower lf-surface distinctly stipitate, with 9-13 subequal branches, and the infl is commonly branched from the top of the peduncle, forming 2 or 3 raceme-like clusters. (S. torreyi)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.