Euphorbia radians |
Euphorbia micromera |
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sun spurge |
desert spurge, Sonoran sandmat, tiny sandmat |
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Habit | Herbs, perennial, with moniliform tuberous rootstock. | Herbs, annual, with slender taproot. |
Stems | erect, 5–20(–30) cm, usually glabrous, occasionally puberulent; branches ± straight. |
prostrate, mat-forming, 5–35 cm, glabrous or shortly pilose. |
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. |
opposite; stipules distinct, subulate, 0.2–0.4 mm, pilose; petiole 0.5–1.2 mm, glabrous or pilose; blade ovate to elliptic, 6–15 × 2–4 mm, base asymmetric, one side cuneate to rounded, other side rounded, margins entire, apex obtuse, surfaces glabrous or pilose; venation obscure or only midvein conspicuous. |
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. |
campanulate, 0.4–0.6 × 0.5–0.9 mm, glabrous or pilose; glands 4, red, circular to oblong, 0.1 × 0.1–0.2 mm; appendages absent. |
Staminate flowers | 20–25. |
2–5. |
Pistillate flowers | ovary glabrous or puberulent, styles 3–4 mm, 2-fid 1/2 to nearly entire length. |
ovary usually glabrous, rarely pilose; styles 0.1–0.2 mm, 2-fid at apex. |
Capsules | depressed-globose, 3.8–5 × 4–5 mm, 3-lobed, glabrous or puberulent; columella 3.6–4.5 mm. |
oblong, 1.3–1.5 × 1.1–1.3 mm, usually glabrous, rarely pilose; columella 1–1.2 mm. |
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. |
light gray, narrowly ovoid, 4-angled in cross section, 0.9–1 × 0.5–0.6 mm, smooth to slightly rugose or with 1–4 faint transverse ridges that do not pass through abaxial keel. |
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. |
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Cyathia | peduncle 2–5.5 mm. |
solitary at distal nodes; peduncle 0.4–1.4 mm. |
Euphorbia radians |
Euphorbia micromera |
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Phenology | Flowering and fruiting spring–summer. | Flowering nearly year-round in response to sufficient rainfall. |
Habitat | Pinyon-juniper woodlands, oak savannas, desert grasslands and scrub. | Desert scrub, riparian woods with ash and willow, saltbush scrub, Joshua tree woodlands and grasslands, often in sandy or gravelly areas. |
Elevation | 700–2500 m. (2300–8200 ft.) | -20–1800 m. (-100–5900 ft.) |
Distribution |
AZ; TX; Mexico
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AZ; CA; NM; NV; TX; UT; Mexico (Baja California, Baja California Sur, Chihuahua, Coahuila, Durango, Sonora)
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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.) |
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Source | FNA vol. 12, p. 324. | FNA vol. 12, p. 278. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Poinsettia | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | Poinsettia radians | Chamaesyce micromera |
Name authority | Bentham: Pl. Hartw., 8. (1839) | Boissier: Proc. Amer. Acad. Arts 5: 171. (1861) |
Web links |