Euphorbia albomarginata |
Euphorbia austrotexana |
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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, usually branched near base, 6–22 cm, glabrous. |
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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 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 | 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, 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 | 15–30. |
5–10. |
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Pistillate flowers | ovary glabrous; styles 0.3–0.7 mm, 2-fid nearly entire length. |
ovary glabrous; styles 0.3–0.5 mm, 2-fid. |
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Capsules | broadly ovoid, 1.1–2.3 × 1.2–2 mm, glabrous; columella 1.1–1.6 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 to gray or brownish red, oblong-ovoid, 4-angled in cross section, 1–1.7 × 0.5–0.8 mm, smooth. |
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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Cyathia | solitary at distal nodes; peduncle 1–4 mm. |
peduncle 0–0.5 mm. |
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Cyathial | 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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Euphorbia albomarginata |
Euphorbia austrotexana |
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Phenology | Flowering and fruiting year-round. | |||||
Habitat | Disturbed areas in desert scrub, grasslands, mesquite woodlands, chaparral. | |||||
Elevation | 0–2300 m. (0–7500 ft.) | |||||
Distribution |
AZ; CA; CO; NM; NV; OK; TX; UT; Mexico [Introduced in Pacific Islands (Hawaii)]
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TX |
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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.) |
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. 259. | FNA vol. 12, p. 298. | ||||
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > subg. Esula | ||||
Sibling taxa | ||||||
Subordinate 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: 634, figs. 1, 2[row 3, left & center]. (2013) | ||||
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