Euphorbia bilobata |
Euphorbia trachysperma |
|
---|---|---|
black-seed spurge |
San Pedro River 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). |
erect to ascending, 10–55 cm, glabrous. |
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 distinct, narrowly triangular and often divided into 3–5 subulate to filiform segments, 0.8–1.9 mm, glabrous; petiole 1.2–3.1 mm, glabrous; blade oblong, elliptic, or ovate, 12–43 × 3–14 mm, base subsymmetric to asymmetric, rounded, attenuate, or with one side hemicordate and other side rounded, margins usually serrulate, rarely entire on some leaves or portion of blade, apex obtuse to acute, surfaces often with red blotch in center, glabrous; pinnately veined, often 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. |
oblong, campanulate, or funnel-shaped, 1.5–2.6 × 1.1–2.3 mm, glabrous; glands 4, green to yellowish or tinged with red, subcircular to oblong, 0.4–0.7 × 0.5–1 mm; appendages absent or white, often forming narrow rim or oblong to ovate, 0–0.8 × 1.2 mm, distal margin entire. |
Staminate flowers | 20–25. |
50–60. |
Pistillate flowers | ovary glabrous, puberulent, strigillose, or pilose; styles 0.5–0.8 mm, 2-fid 1/3–1/2 length. |
ovary glabrous; styles 0.5–0.6 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, 2.4–3.2 × 3–3.5 mm, glabrous; columella 2.3–2.5 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. |
light brown, ovoid, 4-angled in cross section, abaxial keel well developed, 1.9–2.3 × 1.3–1.4 mm, finely dimpled and papillate. |
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 1.4–2.4 mm. |
2n | = 32. |
|
Euphorbia bilobata |
Euphorbia trachysperma |
|
Phenology | Flowering and fruiting spring–fall. | Flowering and fruiting late summer–early winter. |
Habitat | Sandy and rocky soils on slopes and canyon bottoms in pine-juniper woodlands, oak woodlands, grasslands. | Desert scrub, desert grasslands, mesquite woodlands. |
Elevation | 1400–2600 m. (4600–8500 ft.) | 200–1200 m. (700–3900 ft.) |
Distribution |
AZ; NM; TX; Mexico (Chihuahua, Durango, Sonora)
|
AZ; Mexico (Baja California Sur, Sonora) |
Discussion | In Texas, Euphorbia bilobata is known only from Jeff Davis County. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Euphorbia trachysperma may be expected in extreme southwestern New Mexico given the close proximity of some collections in southeastern Arizona. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 243. | FNA vol. 12, p. 291. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Alectoroctonum | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | Chamaesyce trachysperma | |
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): 189. (1859) |
Web links |