N. rustica L., a smaller sp. (to 1 m) with fls 1.5-2 cm, the wide tube dilated from below the top of the cal, the limb greenish-yellow, was cult. by Amerindians, but is now very rare or extinct in our range.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.