Euphorbia ocellata |
Euphorbia revoluta |
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Contura Creek sandmat, Contura Creek spurge, valley spurge |
revolute spurge, threadstem sandmat, threadstem spurge |
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Habit | Herbs, annual, with taproot. | Herbs, annual, with slender taproot. | ||||
Stems | prostrate, 10–35 cm, glabrous or pilose. |
erect, 5–25 cm, glabrous. |
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Leaves | opposite; stipules distinct, subulate, 0.5–1.6 mm, glabrous or pilose; petiole 0.3–2 mm, glabrous or pilose; blade ovate to deltate or falcate, 2.3–13 × 1.5–6 mm, base asymmetric, usually cordate, rarely rounded, margins occasionally reddish, entire, often revolute, apex acute to obtuse, occasionally mucronate, surfaces glabrous or pilose; midvein conspicuous, lateral veins frequently visible abaxially. |
opposite; stipules distinct, subulate-filiform, entire, 0.5–0.9 mm, glabrous; petiole 0.6–1.1 mm, glabrous; blade linear, 6–27 × 0.6–1.2 mm, base symmetric, attenuate, margins entire, revolute, apex acute, sometimes mucronate, surfaces glabrous; only midvein conspicuous. |
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Involucre | campanulate, 1–2.5 × 1.3–2.4 mm, glabrous or pilose; glands 4, yellow becoming deep red, elliptic or oblong to orbiculate, 0.4–0.6 × 0.5–0.7 mm; appendages absent or whitish, orbiculate, 0.1–0.2 × 0.3–0.5 mm, distal margin entire. |
obconic to campanulate, 0.7–0.9 × 0.5–0.7 mm, glabrous; glands 4, pink to dark purple, nearly circular to oblong or reniform, 0.1 × 0.1–0.2 mm; appendages white, oblong, nearly circular, ovate, deltate, or forming thin margin around gland, rarely absent, (0–)0.1–0.2 × (0–)0.1–0.3 mm, distal margin entire. |
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Staminate flowers | 30–70. |
5–10. |
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Pistillate flowers | ovary glabrous or pilose; styles 0.4–0.5 mm, 2-fid at apex. |
ovary glabrous; styles 0.2–0.3 mm, unbranched. |
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Capsules | subglobose to broadly ovoid, 1.4–2.7 × 1.9–3.1 mm, glabrous or pilose; columella 1.4–2 mm. |
ovoid to subglobose, 1.5–1.8 × 1.6–1.8 mm, glabrous; columella 1.1–1.5 mm. |
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Seeds | whitish gray to black, ovoid to oblong, terete to bluntly subangled in cross section, 1.1–1.7 × 0.8–1.3 mm, rugose or smooth. |
whitish, brick red, light gray, or light brown, narrowly to broadly ovoid, 4-angled in cross section, 0.9–1.4 × 0.7–1 mm, nearly smooth, rugulose, with faint transverse ridges, or with 2–3 well-defined transverse ridges separated by shallow depressions. |
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Cyathia | solitary at distal nodes; peduncle 0.9–2.2 mm. |
solitary at distal nodes; peduncles absent or to 1.5 mm. |
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Euphorbia ocellata |
Euphorbia revoluta |
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Phenology | Flowering and fruiting summer–late fall. | |||||
Habitat | Desert scrub, sagebrush scrub, juniper woodlands, Joshua tree-pinyon pine woodlands, oak woodlands, grasslands, chaparral, pine-oak forests. | |||||
Elevation | 600–2500 m. (2000–8200 ft.) | |||||
Distribution |
AZ; CA; ID; NV; UT
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AZ; CA; CO; NM; NV; TX; UT; Mexico (Baja California, Chihuahua, Coahuila, Sonora, Zacatecas)
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Discussion | Subspecies 2 (2 in the flora). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Euphorbia revoluta is a distinctive, easily recognizable species by virtue of the combination of unbranched styles and linear leaves with symmetric bases. The species ranges through northern Mexico into the southwestern United States and is composed of three well-marked, geographically distinct races that can be distinguished by their seeds. The first of these races occurs primarily in pine-oak forest of the Sierra Madre Occidental of Mexico (Chihuahua and Sonora) and barely enters the flora area in the Huachuca Mountains of southeastern Arizona; the seeds are brick red and nearly smooth. The second race is widespread in the Chihuahuan Desert from northern Mexico to southeastern New Mexico and southwestern Texas; its seeds are whitish to light gray and possess two or three well-defined transverse ridges separated by shallow depressions. The third race corresponds to the type collection and is characterized by grayish white to light brown seeds that are rugulose or with faint transverse ridges; it occurs in northwestern Mexico (Baja California and Sonora) and throughout the arid southwestern United States. It is probable that further study will justify the taxonomic segregation of these races as either distinct species or subspecies. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 12, p. 279. | FNA vol. 12, p. 286. | ||||
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > sect. Anisophyllum | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Chamaesyce ocellata | Chamaesyce revoluta | ||||
Name authority | Durand & Hilgard: Pl. Heermann., 46. (1854) | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 186. (1859) | ||||
Web links |