Annual, 2-10 dm, glabrous, or with a few short appressed hairs especially on the younger parts; lvs mostly 4-10 cm, ovate to lance-ovate, irregularly and often coarsely toothed to entire; cor yellowish, not dark in the center, 4-10 mm; anthers 1-2.3 mm; 2n=24, 48. Tropical Amer., n. to se. Va. and Mo., and rarely adventive northward. Summer. Var. angulata, with essentially the range of the sp., has pedicels 5-15 mm in fl, 20-30 mm in fr, the cal-teeth 2-2.5 mm in fl, the mature cal 2.5-3.5 cm. The well marked var. pendula (Rydb.) Waterf., of Mo. to Kans. and Tex., and occasionally intr. eastward, has pedicels 15-40 mm in fl, 20-40 mm in fr, the cal-teeth 1 mm in fl, the mature cal 2-2.5 cm. (P. pendula)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.