Annual; stems prostrate to ascending, branched from the base, usually glabrous or nearly so, 2-5 dm; stipules deeply incised; lfls triangular-obovate, 6-15 mm, two-thirds as wide, obtuse to retuse, glabrous, or obscurely villosulous beneath; peduncles about equaling the subtending petioles; fls yellow, mostly 2-5(-8) per head, 2.5-4 mm; fr 2-5 times spirally coiled, 4-6 mm wide excluding the spines, these 2-3 mm, arising in 2 rows from an elevated ridge, minutely hooked at the tip; 2n=14. Native of the Mediterranean region, now established as a weed in s. U.S. and the Pacific states, and occasionally adventive in our range. Summer. (M. hispida)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.