Euphorbia chamaesula |
Euphorbia abramsiana |
|
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mountain spurge |
Abrams' sandmat, Abrams' spurge |
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Habit | Herbs, perennial, with thick rootstock. | Herbs, annual, with slender taproot. |
Stems | erect, branched, 40–90 cm, glabrous. |
prostrate, mat-forming, 10–35(–50) cm, shortly pilose or puberulent at least proximally, often glabrous distally. |
Leaves | petiole 0.5–1 mm; blade elliptic to oblong, 8–20(–40) × 3–6 mm, base truncate, rounded, or attenuate, margins entire, apex obtuse or acute, sometimes slightly mucronate, surfaces glabrous; venation inconspicuous, only midvein prominent. |
opposite; stipules distinct, divided into 5–7 subulate-filiform segments, 0.6–1.1 mm, usually glabrous, rarely pilose; petiole 0.5–1 mm, glabrous; blade ovate, elliptic-oblong, or slightly ovate-cordate, 3–11 × 2–5 mm, base asymmetric, truncate to hemicordate, margins serrulate at least toward apex, often entire toward base, apex acute to obtuse, surfaces sometimes with red spot in center, glabrous; usually only the midvein conspicuous. |
Involucre | turbinate or campanulate, 1.5–2.5 × 1.1–1.9 mm, glabrous; glands 4, crescent-shaped to semicircular, 0.5–0.8 × 1–1.8 mm; horns usually convergent, 0.2–0.8 mm. |
obconic, 0.5–0.6 × 0.4–0.5 mm, glabrous; glands 4, yellowish to pink, circular to oblong, 0.1 × 0.1–0.2 mm; appendages absent, or white to pink, semicircular to broadly ovate, to 0.1 × 0.2 mm, distal margin entire or shallowly lobed. |
Staminate flowers | 8–12. |
3–5. |
Pistillate flowers | ovary glabrous; styles 1–1.8 mm, 2-fid. |
ovary glabrous; styles 0.1–0.3 mm, 2-fid nearly entire length. |
Capsules | depressed-ovoid, 4.3–5 × 5–6 mm, 3-lobed; cocci rounded, smooth, glabrous; columella 3.5–4 mm. |
ellipsoid to ovoid, 1.3–1.5 × 1.1–1.5 mm, glabrous; columella 1–1.3 mm. |
Seeds | gray to dark brown, ovoid-oblong, truncate at both ends, 2.6–3.4 × 2–2.6 mm, shallowly pitted to almost smooth; caruncle conic, 1 × 0.8 mm. |
light gray to light brown, narrowly ovoid to ovoid, 4-angled in cross section, 1–1.2 × 0.6–0.7 mm, with 3–5 prominent transverse ridges that often interrupt abaxial keel. |
Cyathial | arrangement: terminal pleiochasial branches 3–5(–6), each 3–4 times 2-branched; pleiochasial bracts ovate-lanceolate to slightly subpandurate, similar in size or wider than distal leaves; dichasial bracts distinct, lanceolate to broadly ovate, base usually truncate to rounded or subcordate, sometimes attenuate, margins entire or slightly crenulate, apex usually obtuse to acute, occasionally acuminate; axillary cymose branches 2–8. |
|
Cyathia | peduncle 1–3 mm. |
solitary at distal nodes of primary stems or at nodes of short congested axillary branchlets; peduncle 0.2–0.5 mm. |
2n | = 26. |
|
Euphorbia chamaesula |
Euphorbia abramsiana |
|
Phenology | Flowering and fruiting spring–summer. | Flowering and fruiting summer–fall. |
Habitat | Clearings in ponderosa pine forests, montane roadsides, dry streambeds, creek banks, sandy and gravelly soils. | Desert scrub and desert grasslands. |
Elevation | 1700–2700 m. (5600–8900 ft.) | -40–1400 m. (-100–4600 ft.) |
Distribution |
AZ; NM; Mexico (Chihuahua, Sonora)
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AZ; CA; NM; TX; Mexico (Baja California, Baja California Sur, Sonora)
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Discussion | Euphorbia chamaesula is easily distinguished from other perennial members of subg. Esula in western North America by its larger capsules and the vegetative shoots (without cyathia) that arise from the distal nodes of the stem proximal to the pleiochasia. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
|
Source | FNA vol. 12, p. 300. | FNA vol. 12, p. 259. |
Parent taxa | Euphorbiaceae > Euphorbia > subg. Esula | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | Tithymalus chamaesula | Chamaesyce abramsiana |
Name authority | Boissier: Cent. Euphorb., 38. (1860) | L. C. Wheeler: Bull. S. Calif. Acad. Sci. 33: 109. (1934) |
Web links |