Annual, 1-3 dm, usually much branched; cauline lvs oblong-obovate or subrotund, usually petiolate, 1-2 cm, rounded to retuse at the summit, those subtending the umbel broadly ovate to obovate, those of the umbel smaller, ovate; rays of the umbel 3, repeatedly dichotomous; fr with 2 low longitudinal keels on each valve; seeds 1.5 mm, marked on the outer face with 4 rows of (2)3 or 4 large pits, on the inner face with 2 deep longitudinal furrows; 2n=16. Native of Eurasia, widely intr. in N. Amer. from N.B. to Alas., s. to Fla. and Calif., but seldom abundant. Summer. (Tithymalus p.; Galarhoeus p.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.