Euphorbia exstipulata |
Euphorbia cuphosperma |
|
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square-seed spurge, squareseed or Clark Mountain spurge |
hairy-fruit spurge |
|
Habit | Herbs, annual, with slender taproot. | Herbs, annual, with taproot. |
Stems | erect, 5–26 cm, uniformly puberulent to hispidulous or glabrous; branches arcuate. |
erect, 13–20 cm, both pilose to villous and densely strigillose; branches ± straight. |
Leaves | opposite; petiole 1–3 mm, often indistinct, glabrous or puberulent; blade linear to narrowly elliptic or ovate, 14–42 × 3–28 mm, base attenuate, margins coarsely serrate, occasionally revolute, apex acute to obtuse, abaxial surface sparsely hispidulous to strigillose, adaxial surface glabrous; midvein conspicuous. |
usually opposite, occasionally alternate at distal nodes; petiole 3–15 mm, pilose; blade narrowly to broadly elliptic, or lanceolate to ovate, 30–80 × 10–15 mm, base cuneate to rounded, margins coarsely crenate-dentate, strigose, revolute to nearly flat, apex broadly acute to acuminate, or obtuse, abaxial surface pilose, adaxial surface sparsely strigose-hirsute; venation pinnate, midvein prominent. |
Involucre | turbinate to campanulate, 1.1–1.5 × 1–1.3 mm, glabrous, pilose or puberulent; involucral lobes divided into several linear lobes; glands 4(–5), yellow to pink, sessile and broadly attached, 0.2 × 0.3–0.4 mm, opening oblong to nearly circular, glabrous; appendages usually petaloid, white to pink, ovate to trapezoidal, occasionally absent, not incurved and covering glands, 0.2–0.4 × 0.3–0.8 mm, entire, undulate, or conspicuously divided into triangular segments, glabrous. |
campanulate to slightly cylindric, 2.3 × 1.2 mm, glabrous; involucral lobes divided into several linear, smooth lobes; gland 1, yellow-green, stipitate, clavate, 1–1.2 × 0.8–0.9 mm, opening bilabiate and oblong, glabrous; appendages absent. |
Staminate flowers | 10–12. |
3–5. |
Pistillate flowers | ovary puberulent on keels, styles 0.8–1.1 mm, 2-fid 1/2 to nearly entire length. |
ovary pilose; styles 1.2 mm, 2-fid nearly entire length. |
Capsules | broadly depressed-oblong to ovoid, 2.7–3.3 × 3.1–3.9 mm, puberulent (with appressed hairs usually concentrated on keels); columella 1.9–2.5 mm. |
broadly ovoid, 2.2–3 × 1.9–2.7 mm, 3-lobed, pilose; columella 2–2.4 mm. |
Seeds | white to gray or light brown, ovoid, bluntly 4-angled in cross section, 1.9–2.5 × 1.4–1.7 mm, tuberculate, often with 2 transverse ridges; caruncle 0.1 × 0.2 mm. |
gray-brown to pale gray, pyramidally ovoid, angular in cross section, 2.3–2.6 × 2.4–2.6 mm, coarsely tuberculate, tubercles in 2 transverse rows; caruncle 0.2–0.4 mm. |
Cyathial | arrangement: terminal cymose or dichasial branches usually 1–2, occasionally reduced to monochasia, 1–2-branched; pleiochasial bracts 2–4, often whorled, wholly green or paler green at base, similar in shape and size to distal leaves or slightly narrower; dichasial bracts similar in shape to distal leaves but smaller or highly reduced. |
arrangement: terminal pleiochasial branches usually 3, occasionally reduced to congested cyme, 1–2-branched; pleiochasial bracts 2–4, often whorled, wholly green or paler green at base, similar in shape and size to distal leaves or slightly narrower; dichasial bracts highly reduced. |
Cyathia | peduncle 1–1.9 mm. |
peduncle 0.5–0.8 mm. |
2n | = 56. |
|
Euphorbia exstipulata |
Euphorbia cuphosperma |
|
Phenology | Flowering and fruiting summer–fall. | Flowering and fruiting summer–fall. |
Habitat | Desert scrub, grasslands, mesquite savannas, oak and oak-juniper woodlands. | Open montane and canyon forests, pinyon-juniper forests, montane grasslands, stream beds, disturbed habitats. |
Elevation | 800–2000 m. (2600–6600 ft.) | 800–2000 m. (2600–6600 ft.) |
Distribution |
AZ; CA; NM; TX; UT; WY; Mexico (Chihuahua, Coahuila, Durango, Guanajuato, San Luis Potosí, Sonora, Zacatecas)
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AZ; NM; Mexico; Central America (Guatemala)
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Discussion | Euphorbia exstipulata is native from Texas to California and northern Mexico. The species was found once in the late nineteenth century in Wyoming but has not been re-collected there. Broad-leaved plants have been segregated as var. lata, but the variation in leaf shape is continuous and no varieties are formally recognized here. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
|
Source | FNA vol. 12, p. 322. | FNA vol. 12, p. 319. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Poinsettia | Euphorbiaceae > Euphorbia > sect. Poinsettia |
Sibling taxa | ||
Synonyms | E. exstipulata var. lata | E. dentata var. cuphosperma, Poinsettia cuphosperma |
Name authority | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 189. (1859) | (Engelmann) Boissier: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 15(2): 73. (1862) |
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