Euphorbia spathulata |
Euphorbia theriaca |
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prairie spurge, reticulate seed spurge, spatulate leaf spurge, warty spurge |
Terlingua sandmat, Terlingua 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 to reclining, not mat-forming, 5–30 cm, glabrous. |
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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 usually distinct, occasionally connate basally on lower side of stem, subulate or scalelike, usually entire, occasionally 2-fid or margin sparsely ciliate, 0.4–1 mm, glabrous; petiole 0.7–1.2(–1.5) mm, glabrous; blade ovate, oblong, orbiculate, or obovate, 2–7.1 × 1–3.5 mm, base slightly asymmetric, rounded, margins entire, often revolute on drying, apex usually rounded, occasionally slightly emarginate, surfaces glabrous; venation usually obscure, only midvein conspicuous. |
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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. |
usually turbinate-campanulate to hemispheric, occasionally suburceolate, 1–1.8 × 0.9–1.4 mm, glabrous; glands 4, yellow-green to red-purple, sessile or short-stipitate, subcircular to slightly elliptic, 0.2–0.5 × 0.2–0.7 mm; appendages absent or white to pink, semilunate or forming rim at edge of gland, (0–)0.1–0.4 × (0–)0.3–0.9 mm, entire or slightly crenate. |
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Staminate flowers | 3–10. |
15–36. |
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Pistillate flowers | ovary glabrous; styles 0.8–1.5 mm, 2-fid. |
ovary glabrous; styles 0.3–0.5 mm, 2-fid 1/2 length. |
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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. |
broadly ovoid, 1.1–1.6 × 1.5–1.8 mm, glabrous; columella 1.2–1.5 mm. |
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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. |
whitish, reddish brown beneath coat, ovate, 4-angled in cross section, 0.8–1.2 × 0.5–0.8 mm, with (2–)3(–5) deep transverse ridges. |
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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. |
usually solitary at distal nodes, rarely clustered on short, axillary branches; peduncle 0.3–1.3 mm. |
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2n | = 28. |
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Euphorbia spathulata |
Euphorbia theriaca |
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Phenology | Flowering and fruiting spring–summer. | |||||
Habitat | Forests, fallow fields, prairies, pastures, glades, stream banks, waste places, roadsides. | |||||
Elevation | 0–3500 m. (0–11500 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; TX; n Mexico
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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.) |
Varieties 2 (2 in the flora). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 12, p. 309. | FNA vol. 12, p. 290. | ||||
Parent taxa | Euphorbiaceae > Euphorbia > subg. Esula | Euphorbiaceae > Euphorbia > sect. Anisophyllum | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | E. arkansana, E. dictyosperma, E. obtusata, Galarhoeus arkansanus, G. obtusatus, Tithymalus arkansanus, T. dictyospermus, T. obtusatus, T. spathulatus | Chamaesyce theriaca | ||||
Name authority | Lamarck: in J. Lamarck et al., Encycl. 2: 428. (1788) | L. C. Wheeler: Rhodora 43: 242, plate 660, fig. A. (1941) | ||||
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