Euphorbia radians |
Euphorbia austrotexana |
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sun spurge |
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Habit | Herbs, perennial, with moniliform tuberous rootstock. | Herbs, annual, with taproot. | ||||
Stems | erect, 5–20(–30) cm, usually glabrous, occasionally puberulent; branches ± straight. |
erect, usually branched near base, 6–22 cm, glabrous. |
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Leaves | alternate; petiole 0–2 mm, glabrous or strigose; blade linear-lanceolate to ovate or broadly elliptic, 25–50 × 3–20 mm, unlobed, base rounded (tapered to petiole), margins with few glandular teeth, strigillose, flat to revolute, apex acute, abaxial surface coarsely strigose, adaxial surface strigose-hirsute; venation pinnate, midvein prominent. |
petiole absent; blade linear to slightly lanceolate or linear-oblanceolate, 5–18 × 0.5–2.5 mm, base linear attenuate, margins entire, apex rounded to obtuse or acute, surfaces glabrous; venation pinnate, midvein prominent. |
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Involucre | broadly globose-cupulate, 1.7–2.1 × 2.2–2.5 mm, glabrous or puberulent; involucral lobes divided into triangular segments; glands 1–4(–5), white, sessile and broadly attached, 1.1 × 1.4 mm, opening oblong, glabrous; appendages absent. |
infundibular, 0.8–1.1 × 0.6–0.9 mm, glabrous; glands 4, crescent-shaped; 0.2–0.4 × 0.5–0.6 mm; horns divergent, 0.5–0.7 mm. |
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Staminate flowers | 20–25. |
5–10. |
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Pistillate flowers | ovary glabrous or puberulent, styles 3–4 mm, 2-fid 1/2 to nearly entire length. |
ovary glabrous; styles 0.3–0.5 mm, 2-fid. |
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Capsules | depressed-globose, 3.8–5 × 4–5 mm, 3-lobed, glabrous or puberulent; columella 3.6–4.5 mm. |
ovoid-globose, 1.8–2.2 × 3–3.2 mm, slightly 3-lobed; cocci rounded, smooth, glabrous; columella 1.5–2 mm. |
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Seeds | white, mottled brown to gray, ellipsoid, rounded in cross section, 4–4.6 × 2.4–3.2 mm, smoothly and broadly pitted or grooved; caruncle 0.1 mm. |
white to gray, ellipsoid, 1.4–1.7 × 1–1.3 mm, with deep, irregular to rounded, shallow to concave depressions over entire surface; caruncle reniform-ovate, depressed-conic, 0.5–0.7 × 0.7–1 mm. |
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Cyathial | arrangement: terminal pleiochasial branches usually 3, occasionally reduced to congested cyme, 1–2-branched (often highly condensed); pleiochasial bracts 6–8(–10), as tight involucrate whorl, wholly white to pale pink or red, usually narrower than distal leaves; dichasial bracts linear and highly reduced. |
arrangement: terminal pleiochasial branches 3, 1–3 times 2-branched; pleiochasial bracts similar in shape to but slightly shorter and wider than distal leaves; dichasial bracts distinct, not imbricate, reniform-ovate to subdeltate-ovate or broadly ovate-lanceolate, base obliquely truncate to rounded, margins entire, apex obtuse to broadly acuminate; axillary cymose branches 0–3. |
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Cyathia | peduncle 2–5.5 mm. |
peduncle 0–0.5 mm. |
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Euphorbia radians |
Euphorbia austrotexana |
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Phenology | Flowering and fruiting spring–summer. | |||||
Habitat | Pinyon-juniper woodlands, oak savannas, desert grasslands and scrub. | |||||
Elevation | 700–2500 m. (2300–8200 ft.) | |||||
Distribution |
AZ; TX; Mexico
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TX |
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Discussion | Euphorbia radians is widely distributed but scattered from the Sonoran and Chihuahuan deserts south to Oaxaca in Mexico. The species is distinct among species in sect. Poinsettia in the flora area in its precocious habit, often flowering before the leaves emerge. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Varieties 2 (2 in the flora). Euphorbia austrotexana occurs in stabilized sandy soil in the south Texas plains (M. H. Mayfield 2013). It is similar to E. longicruris but differs from that species in its often narrowly oblanceolate to linear leaves and its white to gray, ellipsoid seeds that are covered with minute, concave depressions. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 12, p. 324. | FNA vol. 12, p. 298. | ||||
Parent taxa | Euphorbiaceae > Euphorbia > sect. Poinsettia | Euphorbiaceae > Euphorbia > subg. Esula | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Poinsettia radians | |||||
Name authority | Bentham: Pl. Hartw., 8. (1839) | Mayfield: J. Bot. Res. Inst. Texas 7: 634, figs. 1, 2[row 3, left & center]. (2013) | ||||
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