Euphorbia spathulata |
Euphorbia rayturneri |
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prairie spurge, reticulate seed spurge, spatulate leaf spurge, warty spurge |
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Habit | Herbs, usually annual, rarely biennial, with taproot. | Herbs, annual, with slender taproot. |
Stems | erect or ascending, unbranched or branched, 10–70 cm, glabrous. |
prostrate, 4–8 cm, uniformly strigillose. |
Leaves | petiole absent or to 0.2 mm; blade oblanceolate, oblong-oblanceolate, spatulate, or cuneate, 10–50 × 6–11 mm, base broadly attenuate to rounded or shallowly cordate-clasping, margins finely serrulate (usually distally), apex usually rounded to obtuse, occasionally slightly retuse or obcordate proximally, bluntly mucronate, surfaces glabrous; venation pinnate, midvein prominent. |
opposite; stipules distinct, filiform, 0.6–0.9 mm, pilose; petiole 0.5–0.9 mm, strigillose; blade ovate to elliptic, often slightly falcate, 5–11 × 2–5 mm, base asymmetric, one side cordate, other round to attenuate, margins sharply serrulate, apex acute, surfaces often with red spot toward middle, abaxial surface strigillose, adaxial surface glabrescent; only midvein conspicuous. |
Involucre | campanulate to cupulate, 0.6–1(–1.5) × 0.8–1.2 mm, glabrous; glands 4–5, elliptic, oblong, to slightly reniform, 0.2–0.6 × 0.4–1 mm; horns absent. |
obconic, 0.9–1.2 × 0.8–1.2 mm, strigillose; glands 4, green, yellow, or light pink, circular to oblong, 0.2 × 0.2–0.3 mm; appendages absent or green, yellow, or light pink, forming narrow margin on distal portion of gland, 0–0.1 × 0.2–0.3 mm, distal margin entire. |
Staminate flowers | 3–10. |
5–8. |
Pistillate flowers | ovary glabrous; styles 0.8–1.5 mm, 2-fid. |
ovary strigillose-canescent; styles 0.3–0.4 mm, unbranched. |
Capsules | depressed-globose, 2–3.5 × 4 mm, 3-lobed; cocci rounded, verrucose, verrucae 0.1–0.2 mm, glabrous; columella 1.4–2.2 mm. |
oblate, 1.7–2 × 2.2–2.7 mm, strigillose; columella 1.5–1.9 mm. |
Seeds | red-brown to dark purple, occasionally ± glaucous, broadly ellipsoid-ovoid to nearly globose, 1.3–2.5 × 1.5–1.8 mm, smooth, reticulate, or finely low-ridged; caruncle irregularly reniform to round, subconic to lenticular, 0.3–0.4 × 0.5–0.6 mm. |
blackish brown, broadly ovoid, 3-angled in cross section, 1.2–1.4 × 1–1.1 mm, with 2 well-defined transverse ridges that do not pass through abaxial keel. |
Cyathial | arrangement: terminal pleiochasial branches 3(–5), each 1–3 times 2-branched; pleiochasial bracts broadly ovate to ovate-oblong, shorter and wider than distal leaves; dichasial bracts distinct, broadly ovate, ovate-triangular, or ovate-elliptic, base cordate-clasping or subcordate to rounded, margins serrulate, apex rounded to obtuse or acute; axillary cymose branches (0–4)5–12. |
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Cyathia | peduncle 0.3–1(–1.5) mm. |
solitary at distal nodes; peduncle 0.5–1.6 mm. |
2n | = 14. |
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Euphorbia spathulata |
Euphorbia rayturneri |
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Phenology | Flowering and fruiting spring–summer. | Flowering and fruiting late summer–early fall. |
Habitat | Forests, fallow fields, prairies, pastures, glades, stream banks, waste places, roadsides. | Desert grasslands. |
Elevation | 0–3500 m. (0–11500 ft.) | 1400–1700 m. (4600–5600 ft.) |
Distribution |
AL; AR; AZ; CA; CO; DC; FL; GA; IA; ID; IL; IN; KS; KY; LA; MD; MI; MN; MO; MS; MT; NC; ND; NE; NM; OH; OK; OR; PA; SC; SD; TN; TX; UT; VA; WA; WI; WV; WY; ON; Mexico (Chihuahua, Sonora); s South America
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NM |
Discussion | As treated here, Euphorbia spathulata is a wide-ranging and variable species. J. B. S. Norton (1900) recognized a number of segregates (for example, E. arkansana, E. dictyosperma, and E. obtusata) all of which are included here in a broadly defined E. spathulata. The only segregate species that has been widely recognized in regional floras is E. obtusata (for example, M. L. Fernald 1950; T. S. Cooperrider 1995; G. Yatskievych 1999–2013, vol. 2). Authors have generally distinguished the eastern North American E. obtusata from the western E. spathulata by the former's larger seeds (1.7–2.3 mm versus 1.5–1.7 mm) with smooth (versus reticulate) surfaces, larger involucres, red (versus yellow) involucral glands, and cordate-clasping (versus rounded to subcordate) dichasial bracts. Examination of specimens of E. spathulata in the broad sense from throughout North America showed that there is some geographic patterning to seed size and surface sculpturing, but the variation does not segregate cleanly into two discrete taxa. Plants from western North America typically have small seeds (1.5–1.7 mm) with reticulate surfaces, although some western individuals have seeds 1.8–1.9 mm long with reticulate surfaces. Plants from Texas generally have small seeds (1.5–1.6 mm) but with the surfaces either reticulate or completely smooth. Plants from adjacent Louisiana have small seeds with faintly reticulate to almost bumpy surfaces. Plants from eastern North America have larger seeds (2–2.3 mm) with usually smooth surfaces, although individuals from Tennessee and the Carolinas have faintly reticulate surfaces. Involucre height, gland color, and the shape of the dichasial bracts do not segregate with seed size as previous treatments have suggested. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Euphorbia rayturneri is known from only three collections in extreme southwestern New Mexico. Given its close proximity to the Mexican border, the species may also occur in the adjacent states of Chihuahua or Sonora. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 309. | FNA vol. 12, p. 286. |
Parent taxa | Euphorbiaceae > Euphorbia > subg. Esula | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | E. arkansana, E. dictyosperma, E. obtusata, Galarhoeus arkansanus, G. obtusatus, Tithymalus arkansanus, T. dictyospermus, T. obtusatus, T. spathulatus | |
Name authority | Lamarck: in J. Lamarck et al., Encycl. 2: 428. (1788) | V. W. Steinmann & Jercinovic: Novon 22: 482, figs. 1, 2. (2013) |
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