Euphorbia exstipulata |
Euphorbia longicruris |
|
---|---|---|
square-seed spurge, squareseed or Clark Mountain spurge |
wedge-leaf 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, usually unbranched, occasionally branched later in season, 5–25 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 0–0.5 mm; blade cuneate-spatulate to obovate, 5–15 × 2–6 mm, base broadly attenuate, margins entire, apex rounded to obtuse, mucronate, surfaces glabrous; 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, 1.5–2 × 1–1.5 mm, glabrous; glands 4, crescent-shaped to elliptic, 0.4–0.8 × 0.8–1.1 mm; horns divergent, 0.5–0.8 mm. |
Staminate flowers | 10–12. |
10–15. |
Pistillate flowers | ovary puberulent on keels, styles 0.8–1.1 mm, 2-fid 1/2 to nearly entire length. |
ovary glabrous; styles 0.5–0.6 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. |
ovoid-globose, 2–2.8 × 2.5–3 mm, 3-lobed; cocci rounded, smooth, glabrous; columella 1.6–2.1 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 to purple-gray or sometimes nearly black, oblong, 1.3–1.6 × 0.9–1.2 mm, strongly small-pitted; caruncle umbonate, depressed-conic, 0.5 × 0.7 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 3, each many times 2-branched; pleiochasial bracts obovate, similar in size to distal leaves; dichasial bracts basally subconnate, strongly imbricate and often obscuring internodes, reniform to semiorbiculate, base cordate, margins entire, apex rounded; axillary cymose branches 0–5. |
Cyathia | peduncle 1–1.9 mm. |
peduncle 0.3–0.5 mm. |
Euphorbia exstipulata |
Euphorbia longicruris |
|
Phenology | Flowering and fruiting summer–fall. | Flowering and fruiting spring. |
Habitat | Desert scrub, grasslands, mesquite savannas, oak and oak-juniper woodlands. | Grasslands, open prairies, sites with rocky, usually calcareous soils. |
Elevation | 800–2000 m. (2600–6600 ft.) | 300–800 m. (1000–2600 ft.) |
Distribution |
AZ; CA; NM; TX; UT; WY; Mexico (Chihuahua, Coahuila, Durango, Guanajuato, San Luis Potosí, Sonora, Zacatecas)
|
AR; KS; OK; TX |
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.) |
Euphorbia longicruris is quite similar to the other small, annual members of subg. Esula in the south-central United States and can best be distinguished from those species by its imbricate dichasial bracts that form little tufts of overlapping leaves at the ends of the pleiochasial branches. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 322. | FNA vol. 12, p. 304. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Poinsettia | Euphorbiaceae > Euphorbia > subg. Esula |
Sibling taxa | ||
Synonyms | E. exstipulata var. lata | Tithymalus longicruris |
Name authority | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 189. (1859) | Scheele: Linnaea 22: 152. (1849) |
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