Euphorbia exstipulata |
Euphorbia falcata |
|
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square-seed spurge, squareseed or Clark Mountain spurge |
sickle 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, unbranched or branched, 5–20 cm, glabrous. |
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. |
petiole absent; blade obovate, linear-oblong, or spatulate, 2–20 × 2–10 mm, base cuneate or attenuate, margins entire, apex acute, obtuse, emarginate, or mucronate, surfaces glabrous; venation usually inconspicuous, sometimes 3-nerved from base, 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. |
cupulate, 0.5–1.2 × 0.6–1.3 mm, glabrous; glands 4, elliptic to orbiculate, 0.2–0.3 × 0.3–0.8 mm; horns usually absent, occasionally divergent, 0.5–1.2 mm. |
Staminate flowers | 10–12. |
6–10. |
Pistillate flowers | ovary puberulent on keels, styles 0.8–1.1 mm, 2-fid 1/2 to nearly entire length. |
ovary pilose only at base, styles 0.9–1.1 mm, 2-fid. |
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. |
subovoid, 2–3 × 1.8–3 mm, slightly lobed; cocci rounded, smooth, glabrous or slightly pilose along abaxial region; columella 1.1–1.8 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. |
grayish, whitish, or light brownish, ovoid, 1.2–1.8 × 0.7–1.1 mm, transversally sulcate; caruncle subglobose to subconic, 0.2–0.5 × 0.2–0.5 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 2–5, each 2–6 times 2-branched; pleiochasial bracts similar in shape to but usually shorter and wider than distal leaves; dichasial bracts distinct, widely ovate, rhombic, or suborbiculate, imbricate, base cordate, truncate or cuneate, margins finely denticulate, apex acute or obtuse, strongly mucronate; axillary cymose branches 0–10. |
Cyathia | peduncle 1–1.9 mm. |
peduncle 0–2 mm. |
Euphorbia exstipulata |
Euphorbia falcata |
|
Phenology | Flowering and fruiting summer–fall. | Flowering and fruiting spring–summer. |
Habitat | Desert scrub, grasslands, mesquite savannas, oak and oak-juniper woodlands. | Waste places, roadsides. |
Elevation | 800–2000 m. (2600–6600 ft.) | 0–1600 m. (0–5200 ft.) |
Distribution |
AZ; CA; NM; TX; UT; WY; Mexico (Chihuahua, Coahuila, Durango, Guanajuato, San Luis Potosí, Sonora, Zacatecas)
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KY; MD; OH; PA; TN; VA; WV; s Europe; c Europe; w Asia; c Asia; s Asia; n Africa [Introduced in North America; introduced also in South America (Chile)] |
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. 302. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Poinsettia | Euphorbiaceae > Euphorbia > subg. Esula |
Sibling taxa | ||
Synonyms | E. exstipulata var. lata | Tithymalus falcatus |
Name authority | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 189. (1859) | Linnaeus: Sp. Pl. 1: 456. (1753) |
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