Euphorbia chamaesula |
Euphorbia perennans |
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mountain spurge |
perennial sandmat, Terlingua spurge |
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Habit | Herbs, perennial, with thick rootstock. | Herbs, perennial, with strongly thickened, woody rootstock. |
Stems | erect, branched, 40–90 cm, glabrous. |
erect, 7–45 cm, glabrous. |
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, linear-filiform in (1–)2(–3) segments, 0.3–0.4 mm, glabrous; petiole 0.8–2 mm, glabrous; blade ovate or orbiculate-deltate to reniform-deltate, 5–17 × 4–16 mm midstem leaves largest, base symmetric, cuneate, rounded to cordate, margins entire, apex acute to rounded, surfaces glabrous, often glaucous; 3-veined from base, only 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. |
broadly-campanulate to hemispheric, 1.7–2.2 × 1.5–2.7 mm, glabrous; glands 4, green to yellow-green, elliptic to oblong, folded longitudinally, 0.3–0.5 × 0.7–1.4 mm; appendages absent. |
Staminate flowers | 8–12. |
35–45. |
Pistillate flowers | ovary glabrous; styles 1–1.8 mm, 2-fid. |
ovary glabrous; styles 0.7–0.9 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. |
subglobose to broadly ovoid, 2.8–3.3 × 2.8–3.4 mm, glabrous; columella 2.2–2.7 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. |
white to light brown, ovoid, 3–4-angled in cross section, 2–2.4 × 1–1.2 mm, smooth to faintly transverse-wrinkled. |
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 or at nodes of short, axillary branches; peduncle 1.8–3 mm. |
2n | = 26. |
|
Euphorbia chamaesula |
Euphorbia perennans |
|
Phenology | Flowering and fruiting spring–summer. | Flowering and fruiting spring–fall. |
Habitat | Clearings in ponderosa pine forests, montane roadsides, dry streambeds, creek banks, sandy and gravelly soils. | Desert scrub, on cretaceous and gypseous clay, limestone hills and flats. |
Elevation | 1700–2700 m. (5600–8900 ft.) | 900–1200 m. (3000–3900 ft.) |
Distribution |
AZ; NM; Mexico (Chihuahua, Sonora)
|
TX; Mexico (Chihuahua) |
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.) |
Euphorbia perennans is a distinctive species with an erect habit and relatively large, firm, deltate midstem leaves. Phylogenetic data place E. perennans in a clade of primarily Chihuahuan Desert annual and perennial species (for example, E. chaetocalyx, E. fendleri, E. golondrina, E. simulans, E. spurca, and E. theriaca; Y. Yang and P. E. Berry 2011). Euphorbia perennans is known in the flora area only from Brewster County. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 300. | FNA vol. 12, p. 282. |
Parent taxa | Euphorbiaceae > Euphorbia > subg. Esula | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | Tithymalus chamaesula | Chamaesyce perennans |
Name authority | Boissier: Cent. Euphorb., 38. (1860) | (Shinners) Warnock & M. C. Johnston: SouthW. Naturalist 5: 170. (1960) |
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