Euphorbia albomarginata |
Euphorbia georgiana |
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rattlesnake sandmat, rattlesnake weed, white-margin sandmat or sandwort, whitemargin sandmat |
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Habit | Herbs, perennial, with moderately to strongly thickened rootstock. | Herbs, annual, with taproot. |
Stems | prostrate, occasionally mat-forming, frequently rooting at nodes, 10–80 cm, glabrous. |
erect, often branched near base, 10–18 cm, glabrous. |
Leaves | opposite; stipules connate into conspicuous, deltate or ovate scale, white, 0.4–1(–2) mm, glabrous; petiole less than 1 mm, glabrous; blade ovate, oblong or orbiculate, 3–8(–15) × 3–7 mm, base strongly asymmetric, obtuse to hemicordate, margins whitish, entire, apex obtuse, rarely mucronulate, surfaces often with red blotch in center, glabrous; 3-veined from base but usually only midvein conspicuous. |
petiole absent; blade oblanceolate, 5–12 × 3–5 mm, base attenuate, margins entire, apex rounded, surfaces glabrous; venation pinnate, midvein prominent. |
Involucre | campanulate, 0.8–1.1 × 0.9–2 mm, glabrous; glands 4, greenish yellow to red, usually oblong to reniform, rarely subcircular, 0.2–0.5 × (0.2–)0.3–0.8 mm; appendages white to pink, flabellate to oblong, 0.3–1 × 0.6–1.3 mm, distal margin entire or crenulate to erose. |
infundibular, 1–1.1 × 0.4–0.5 mm, glabrous; glands 4, crescent-shaped; 0.3–0.4 × 0.4–0.5 mm; horns divergent, 0.3–0.5 mm. |
Staminate flowers | 15–30. |
5–10. |
Pistillate flowers | ovary glabrous; styles 0.3–0.7 mm, 2-fid nearly entire length. |
ovary glabrous; styles 0.5 mm, 2-fid. |
Capsules | broadly ovoid, 1.1–2.3 × 1.2–2 mm, glabrous; columella 1.1–1.6 mm. |
depressed-ovoid, 2.2–2.4 × 3.2–3.4 mm, 3-lobed; cocci rounded, smooth, glabrous; columella 2–2.1 mm. |
Seeds | white to gray or brownish red, oblong-ovoid, 4-angled in cross section, 1–1.7 × 0.5–0.8 mm, smooth. |
gray, ovoid, 1.6–1.7 × 1.4–1.6 mm, with deep, rounded pits irregularly scattered over entire surface; caruncle reniform, subconic, 0.5–0.6 × 0.6–0.8 mm. |
Cyathia | solitary at distal nodes; peduncle 1–4 mm. |
peduncle 0.3–0.5 mm. |
Cyathial | arrangement: terminal pleiochasial branches 3, 1–3 times 2-branched; pleiochasial bracts rotund-obovate, wider than distal leaves; dichasial bracts distinct, not imbricate, broadly deltate to subreniform, base truncate to emarginate, margins entire, apex rounded to bluntly acuminate; axillary cymose branches 0–1. |
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Euphorbia albomarginata |
Euphorbia georgiana |
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Phenology | Flowering and fruiting year-round. | Flowering and fruiting spring. |
Habitat | Disturbed areas in desert scrub, grasslands, mesquite woodlands, chaparral. | Granite outcrops. |
Elevation | 0–2300 m. (0–7500 ft.) | 100–200 m. (300–700 ft.) |
Distribution |
AZ; CA; CO; NM; NV; OK; TX; UT; Mexico [Introduced in Pacific Islands (Hawaii)]
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GA |
Discussion | Euphorbia albomarginata is native to northern and central Mexico and the southwestern and south-central United States. The species occurs in a variety of habitats in western North America and in some areas is quite weedy. It has been recorded as a waif in Louisiana. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Euphorbia georgiana is restricted to granitic outcrops; it is known from Oglethorpe and Wilkes counties (M. H. Mayfield 2013). It is similar to E. austrotexana but has larger seeds that are much more deeply pitted and leaves that are oblanceolate instead of linear-oblanceolate to linear. It is also quite distinct from the more robust, biennial or occasionally annual E. commutata, the only other closely-related species that occurs in the area. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 259. | FNA vol. 12, p. 303. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > subg. Esula |
Sibling taxa | ||
Synonyms | Chamaesyce albomarginata | |
Name authority | Torrey & A. Gray: in War Department [U.S.], Pacif. Railr. Rep. 2(4): 174. (1857) | Mayfield: J. Bot. Res. Inst. Texas 7: 639, fig. 2[row 2, left]. (2013) |
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