Euphorbia perennans |
Euphorbia brachycera |
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perennial sandmat, Terlingua spurge |
horned spurge, shorthorn spurge |
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Habit | Herbs, perennial, with strongly thickened, woody rootstock. | Herbs, perennial, with thick rootstock. |
Stems | erect, 7–45 cm, glabrous. |
erect or ascending, branched, 10–60 cm, usually glabrous, sometimes puberulent. |
Leaves | 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. |
petiole 0–0.5 mm; blade oblong-elliptic, lanceolate, or oblanceolate to broadly ovate, 5–25 × 2–7 mm, base truncate, rounded, acute, or attenuate, margins entire, apex acute or obtuse, sometimes mucronate, surfaces usually glabrous, sometimes puberulent; venation inconspicuous, only midvein prominent. |
Involucre | 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. |
turbinate, campanulate or cupulate, 1.5–2.6 × 1.4–1.7 mm, usually glabrous, sometimes puberulent; glands 4, crescent-shaped to triangular-ovate, 0.5–0.8 × 0.7–1.7 mm, margins usually entire, occasionally slightly crenate to dentate; horns divergent, 0.2–0.4 mm, longer than teeth on gland margin. |
Staminate flowers | 35–45. |
10–15. |
Pistillate flower(s) | ovary glabrous; styles 0.7–0.9 mm, 2-fid nearly entire length. |
ovary, usually glabrous, sometimes puberulent; styles 0.5–0.9 mm, 2-fid. |
Capsules | subglobose to broadly ovoid, 2.8–3.3 × 2.8–3.4 mm, glabrous; columella 2.2–2.7 mm. |
depressed-ovoid, 2.8–4 × 3.5–4.5 mm, 3-lobed; cocci rounded, smooth, usually glabrous, sometimes sparsely puberulent; columella 2.4–3.3 mm. |
Seeds | white to light brown, ovoid, 3–4-angled in cross section, 2–2.4 × 1–1.2 mm, smooth to faintly transverse-wrinkled. |
light gray, cylindric ovoid-oblong, 2–2.8(–3) × 1.4–2.2 mm, irregularly shallowly pitted; caruncle sessile to shortly stipitate, conic, 0.4–0.5 × 0.8–1.1 mm. |
Cyathia | solitary at distal nodes or at nodes of short, axillary branches; peduncle 1.8–3 mm. |
peduncle 0.4–1 mm. |
Cyathial | arrangement: terminal pleiochasial branches 3–5(–8), 1–4+ times 2-branched; pleiochasial bracts lanceolate or ovate to broadly ovate, wider than distal leaves; dichasial bracts distinct, broadly ovate or rhombic to triangular-ovate, base obtuse, margins entire or slightly crenate, apex obtuse, mucronate; axillary cymose branches 0–8. |
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2n | = 28. |
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Euphorbia perennans |
Euphorbia brachycera |
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Phenology | Flowering and fruiting spring–fall. | Flowering and fruiting spring–summer. |
Habitat | Desert scrub, on cretaceous and gypseous clay, limestone hills and flats. | Montane areas, canyons, rock crevices, sandy or gravelly slopes, pine-oak woodlands, ponderosa pine and mixed coniferous forests. |
Elevation | 900–1200 m. (3000–3900 ft.) | 1200–3200 m. (3900–10500 ft.) |
Distribution |
TX; Mexico (Chihuahua) |
AZ; CO; ID; MT; ND; NE; NM; SD; TX; UT; WY; Mexico (Chihuahua, Coahuila, Sonora)
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Discussion | 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.) |
Euphorbia brachycera is morphologically extremely variable, and plants from the northern part of the species range have sometimes been distinguished as E. robusta. Euphorbia brachycera is most closely related to the other native, perennial species of subg. Esula in western North America, namely E. chamaesula, E. lurida, E. schizoloba, and E. yaquiana. The name E. montana Engelmann, which has sometimes been applied to E. brachycera, is illegitimate because it is a later homonym of E. montana Rafinesque. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 282. | FNA vol. 12, p. 300. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Chamaesyce perennans | E. brachycera var. robusta, E. montana var. robusta, E. odontadenia, E. robusta, Tithymalus brachycerus, T. robustus |
Name authority | (Shinners) Warnock & M. C. Johnston: SouthW. Naturalist 5: 170. (1960) | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 192. (1859) |
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