Stems branched, arched or decumbent, to 1 m long, strongly ribbed, armed with stout hooked prickles; lvs 6-15 cm, the rachis and rachillae prickly; pinnae 3-5(-7) pairs, 1-5 cm; lfls 8-11(-14) pairs, oblong or elliptic, often shortly cuspidate, 1.5-9 mm, the veins few, obscure to very prominent and reticulate beneath; heads long-peduncled, 1.5-2.5 cm thick; fr linear, strongly ribbed, 4-8(-12) cm, prickly on the ribs, the slender beak 0.5-2 cm; 2n=36. Dry, sterile or sandy soil; widespread in tropical and warm-temperate parts of the New World, in the U.S. n. to w. Va., Ky., w. Io., and S.D. May-Sept. Some 11 ±geographic vars., 2 in our range. Var. nuttallii (DC.) Beard ex Barneby, w. of the Mississippi R., has the lateral veins of the lfls prominently raised beneath; its heads are 1.5-2.5 cm thick (7-11 mm without the filaments); and the stems and pods are not hairy. (Schrankia nuttallii; S. uncinata, misapplied; Leptoglottis n.) Var. angustata (Torr. & A. Gray) Barneby, mainly e. of the Mississippi R. and Gulf coastal, has the lateral veins of the lfls obscure; its heads are 1-1.5 cm thick (5-7.5 mm without the filaments); and the stems and pods are often finely puberulent. (Schrankia microphylla; Leptoglottis m.; Moronga m.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.