Euphorbia bilobata |
Euphorbia serrula |
|
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black-seed spurge |
sawtooth sandmat |
|
Habit | Herbs, annual, with slender taproot. | Herbs, annual, with slender taproot. |
Stems | erect, branched, 10–35 cm, glabrous or strigillose (especially when young and around nodes). |
prostrate or ascending, 5–20 cm, usually pilose to villous, rarely glabrate. |
Leaves | opposite proximally, alternate distally; stipules 0.1–0.2 mm; petiole 1–4(–6) mm, glabrous, sericeous or strigillose; blade linear to narrowly elliptic, 8–52 × 2–7 mm, base attenuate, margins entire, ciliate-strigose, apex acute, abaxial surface sparsely strigillose to sericeous, adaxial surface usually glabrous; venation obscure, only midvein conspicuous. |
opposite; stipules usually distinct, rarely connate at base, triangular or laciniate into subulate segments, 1–1.8 mm, glabrous; petiole 0.3–0.8 mm, glabrous or villous; blade oblong, ovate, or elliptic, sometimes falcate, 3–11 × 2–5 mm, base asymmetric, rounded to hemicordate, margins sharply serrate to serrulate, usually with conspicuous teeth at base of leaf, apex usually obtuse, rarely acute, surfaces frequently with red blotch in center, not papillate, sparsely pilose to glabrate; only midvein conspicuous. |
Involucre | obconic, 0.9–1.5 × 0.9–1.3 mm, strigillose to pilose; glands 5, yellow or pink, U-shaped, 0.2–0.3 × 0.4–0.5 mm; appendages greenish, white, or pink, forming narrow rim around gland, or ovate, oblong, or obovate and usually 2-fid, rarely rudimentary, 0.2–1.4 × 0.2–0.6 mm, entire. |
obconic, 0.8–1.1 × 0.8–1 mm, glabrous; glands 4, greenish yellow, usually reniform to elliptic, rarely circular, 0.1 × 0.1–0.2 mm; appendages usually white, rarely light pink, orbiculate, 0.1–0.3 × 0.2–0.4 mm, distal margin entire or crenulate. |
Staminate flowers | 20–25. |
7–15. |
Pistillate flowers | ovary glabrous, puberulent, strigillose, or pilose; styles 0.5–0.8 mm, 2-fid 1/3–1/2 length. |
ovary glabrous; styles 0.3–0.5 mm, 2-fid 1/2 length. |
Capsules | oblate, 1.5–2.6 × 2.1–3.3 mm, glabrous or puberulent, strigillose, or pilose; columella 1.2–2.1 mm. |
oblate, cocci not elongated nor terminating in empty portion, 2–2.6 × 3.2–3.7 mm, glabrous; columella 1.7–2.1 mm. |
Seeds | brown to grayish black, narrowly ovoid, 3- or 4-angled in cross section, sometimes obscurely so, 1.3–1.9 × 1–1.4 mm, tuberculate, often with shallow depressions; caruncle absent. |
white to light brown, broadly ellipsoid to ovoid, 3–4-angled in cross section, 1.5–1.8 × 1.1–1.3(–1.5) mm, smooth to minutely rugulose or with scattered small depressions. |
Cyathia | solitary at distal nodes or in weakly defined cymes or dichasia, dichasial bracts and distal stem leaves wholly green; peduncle 0.5–3.6 mm, strigillose. |
solitary at distal nodes; peduncle 0.4–1.8(–2.3) mm. |
2n | = 32. |
|
Euphorbia bilobata |
Euphorbia serrula |
|
Phenology | Flowering and fruiting spring–fall. | Flowering and fruiting spring–fall. |
Habitat | Sandy and rocky soils on slopes and canyon bottoms in pine-juniper woodlands, oak woodlands, grasslands. | Desert scrub, with creosote bush, grasslands with mesquite and yucca, rarely in ponderosa pine woodlands, often sandy substrates. |
Elevation | 1400–2600 m. (4600–8500 ft.) | 300–1900 m. (1000–6200 ft.) |
Distribution |
AZ; NM; TX; Mexico (Chihuahua, Durango, Sonora)
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AZ; NM; TX; Mexico
|
Discussion | In Texas, Euphorbia bilobata is known only from Jeff Davis County. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
In Mexico, Euphorbia serrula is found from Chihuahua and Coahuila south to Puebla. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 243. | FNA vol. 12, p. 288. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Alectoroctonum | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | Chamaesyce serrula | |
Name authority | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 190. (1859) | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 188. (1859) |
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