Euphorbia missurica Raf.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
Species Description - Glabrous annual; stems decumbent to suberect, 1–6 dm, repeatedly forked; lvs linear to oblong, 1–3 cm, entire, obtuse to rounded or retuse; appendages ovate to oblong, conspicuous, more than twice as long as the glands; stamens 29–48 per involucre; fr strongly 3-lobed, 2–2.5 mm; seeds not compressed, smooth, roundly 3-angled, mottled white and brown, 1.5–2 mm. Rocky or sandy soil; Minn. to Mont., s. to Mo., Tex., and N.M. Summer. Var. missurica (E. zygophylloides; Chamaesyce z.; C. nuttallii), with scarcely angled seeds, capillary smaller branches, and capillary peduncles to 11 mm, occurs from Mo. to Tex. Var. intermedia (Engelm.) L. C. Wheeler (E. petaloidea; Chamaesyce p.) with definitely angled seeds, and stouter branches and peduncles, the latter to 4 mm, occurs from Minn. to Mont. and Tex.