Euphorbia bilobata |
Euphorbia laredana |
|
---|---|---|
black-seed spurge |
Laredo sandmat |
|
Habit | Herbs, annual, with slender taproot. | Herbs, annual, with taproot. |
Stems | erect, branched, 10–35 cm, glabrous or strigillose (especially when young and around nodes). |
prostrate, ± mat-forming, 10–20 cm, densely ashy pilose-tomentose. |
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, filiform, 0.5–1 mm, pilose-tomentose; petiole 0.5–1 mm, pilose-tomentose; blade ovate to elliptic-oblong, 3–6 × 3–5 mm, base markedly asymmetric, rounded to slightly auriculate, margins usually entire, rarely largest leaves sparsely serrulate, apex acute to obtuse, surfaces moderately to densely strigose; 3-veined from base. |
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, 0.6–1 × 0.5–1 mm, densely strigose; glands 4, yellowish to reddish, oval to oblong, 0.1 × 0.2–0.3 mm; appendages white to pink, rudimentary or minute, (0–)0.1–0.2 × (0–)0.1–0.3 mm, distal margin crenulate. |
Staminate flowers | 20–25. |
3–5. |
Pistillate flowers | ovary glabrous, puberulent, strigillose, or pilose; styles 0.5–0.8 mm, 2-fid 1/3–1/2 length. |
ovary densely white villous; styles 0.1–0.2 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. |
broadly ovoid, 1.3–1.5 × 1.4–1.5 mm, villous on keels, often glabrous or less hairy between keels; columella 1.1–1.3 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, barely concealing brown undercoat, 4-angled, sharply angled in cross section, abaxial faces plane to convex, adaxial faces concave, 1.1–1.2 × 0.5–0.7 mm, with several rounded, irregular, transverse ridges. |
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 or in small, cymose clusters at distal nodes or on congested, axillary branches; peduncle 0.5–1.5 mm. |
2n | = 32. |
|
Euphorbia bilobata |
Euphorbia laredana |
|
Phenology | Flowering and fruiting spring–fall. | Flowering and fruiting almost year-round. |
Habitat | Sandy and rocky soils on slopes and canyon bottoms in pine-juniper woodlands, oak woodlands, grasslands. | Open sandy, loamy, or gravelly sites, old dunes, pastures. |
Elevation | 1400–2600 m. (4600–8500 ft.) | 0–200 m. (0–700 ft.) |
Distribution |
AZ; NM; TX; Mexico (Chihuahua, Durango, Sonora)
|
TX; Mexico (Tamaulipas) |
Discussion | In Texas, Euphorbia bilobata is known only from Jeff Davis County. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Euphorbia laredana is similar to E. prostrata but differs from that species in its more densely tomentose indumentum, leaves with usually entire rather than serrulate margins, and slightly longer seeds with rounded rather than sharp ridges. The species occurs primarily in southern Texas. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 243. | FNA vol. 12, p. 274. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Alectoroctonum | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | Chamaesyce laredana | |
Name authority | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 190. (1859) | Millspaugh: Pittonia 2: 88. (1890) |
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