FNA 2016, Allred and Ivey 2012, Correll and Johnston 1970

Duration: Annual Nativity: Native Lifeform: Forb/Herb General: Annual herbs, 20-60 cm tall (rarely up to 1 m tall), from a taproot; stems several, erect or ascending; herbage glabrous and sometimes glaucous.  Leaves: Opposite along the stems, on short petioles 1-3 mm long; blade linear to narrowly oblong, 4-30 mm long and 3-7 mm wide, the wider leaves with noticably asymmetric bases; margins entire; leaf underside lighter green than the upper surface; stipules 1 mm long, usually distinct but occasionally united at the base on one or both sides of stem, deeply and irregularly fringed or lobed. Flowers: Has the highly modified flower structure characteristic of Euphorbias. Structures called cyathia appear to be individual flowers, but are composed of fused-together bracts forming a cup (involucre), with peripheral nectary glands which are often subtended by petal-like bracts called petaloid appendages. Within the cup there is a ring of inconspicuous male flowers, each reduced to a single stamen. Out of the middle protrudes a single, stalked female flower which lacks petals. In E. missurica, the cyathia (flower structures) are solitary or clustered in leaf axils near branch tips; Involucres are broadly bell-shaped, 1.5 mm high, and glabrous, with 4 yellowish-green cup-shaped glands around the edge, each with a white to pinkish petaloid appendage; 24-60 staminate flowers. Fruits: Capsules ovoid-globose and 3-celled, 2 mm high, glabrous; containing 3 mottled-whitish to brown, ovoid-triangular seeds, 2 mm high, bluntly 3-angled in cross section, smooth or slightly wrinkled. Ecology: Found in glades, on ledges, bluff tops (usually calcareous), dry upland forest margins, and sandy or disturbed areas, below 5,000 ft (1524 m); flowers June-November. Distribution: c US, from MT to MN, south to NM, TX, and AR. Notes: This species belongs to the Chamaesyce subgenus of Euphorbia. Some treatments, even recent ones, continue to treat Chamaesyce as a separate genus even though molecular evidence places it within Euphorbia. Chamaesyce spp are distinct based on their leaves which are always opposite and and often have asymmetric bases; cyathia (flower structures) in leaf axils, not at branch tips, and usually with petaloid appendages; and stipules present and not gland-like. E. missurica is distinguished by being a glabrous (hairless) annual with an upright growth form sometimes over half a meter tall (many annual Chamaesyces are prostrate and mat-forming); oblong leaves 4-30 mm long and more than three times as long as wide, with smooth (entire) edges; seed pods 2-3 mm high; and cyathia (flower-like structures) with white petaloid appendages that are larger than the glands they are attached to. Euphorbia missurica is similar to the western E. parryi but has a more upright growth habit and more conspicuous petaloid appendages. It is wise to make a collection whenever ID to species is needed, as Chamaesyces are difficult to identify in the field, and multiple species of the genus will commonly grow side-by-side. Ethnobotany: Unknown Etymology: Euphorbia is named for Euphorbus, Greek physician of Juba II, King of Mauretania; missurica means from missouri. Editor: AHazelton 2017

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.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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