Euphorbia chamaesula |
Euphorbia austrotexana |
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mountain spurge |
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Habit | Herbs, perennial, with thick rootstock. | Herbs, annual, with taproot. | ||||
Stems | erect, branched, 40–90 cm, glabrous. |
erect, usually branched near base, 6–22 cm, glabrous. |
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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. |
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 | 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. |
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 | 8–12. |
5–10. |
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Pistillate flowers | ovary glabrous; styles 1–1.8 mm, 2-fid. |
ovary glabrous; styles 0.3–0.5 mm, 2-fid. |
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Capsules | depressed-ovoid, 4.3–5 × 5–6 mm, 3-lobed; cocci rounded, smooth, glabrous; columella 3.5–4 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 | 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. |
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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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. |
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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Cyathia | peduncle 1–3 mm. |
peduncle 0–0.5 mm. |
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2n | = 26. |
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Euphorbia chamaesula |
Euphorbia austrotexana |
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Phenology | Flowering and fruiting spring–summer. | |||||
Habitat | Clearings in ponderosa pine forests, montane roadsides, dry streambeds, creek banks, sandy and gravelly soils. | |||||
Elevation | 1700–2700 m. (5600–8900 ft.) | |||||
Distribution |
AZ; NM; Mexico (Chihuahua, Sonora)
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TX |
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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.) |
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. 300. | FNA vol. 12, p. 298. | ||||
Parent taxa | Euphorbiaceae > Euphorbia > subg. Esula | Euphorbiaceae > Euphorbia > subg. Esula | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Tithymalus chamaesula | |||||
Name authority | Boissier: Cent. Euphorb., 38. (1860) | Mayfield: J. Bot. Res. Inst. Texas 7: 634, figs. 1, 2[row 3, left & center]. (2013) | ||||
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