Euphorbia arizonica |
Euphorbia bombensis |
|
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Arizona sandmat, Arizona spurge |
Dixie sandmat, southern seaside spurge |
|
Habit | Herbs, annual or short-lived perennial, with slender to slightly thickened taproot. | Herbs, usually annual, rarely perennial, with taproot. |
Stems | erect to ascending, 10–30 cm, uniformly pilose with glistening hairs. |
prostrate or slightly ascending, 10–40 cm, glabrous. |
Leaves | opposite; stipules distinct, deltate, (0–)0.1 mm, glabrous or with few scattered hairs; petiole 0.4–1.5 mm, pilose with glistening hairs; blade usually ovate, rarely elliptic, 3–11 × 2–7 mm, base asymmetric, one side cuneate to rounded, other side rounded to strongly cordate, margins entire, apex obtuse or acute, surfaces pilose with glistening hairs; 3-veined from base but usually only midvein conspicuous. |
opposite; stipules distinct, linear-subulate, usually divided into 3 linear segments, 1–2 mm, glabrous; petiole 1–2 mm, glabrous; blade oblong or elliptic-oblong, 4–15 × 2–3 mm, base asymmetric to nearly symmetric, obtuse, margins entire, apex acute to mucronate, surfaces green to reddish flushed, glabrous; only midvein conspicuous. |
Involucre | urceolate, 1.1–1.3 × 0.5–0.9 mm, glabrous or pilose with glistening hairs; glands 4, dark maroon, usually oblong to reniform, rarely almost circular, 0.2 × 0.2–0.4 mm; appendages white to pink, oblong, flabellate, oblong, or elliptic, 0.3–0.6 × 0.6–0.9 mm, distal margin entire or crenulate. |
obconic-campanulate, 1.2–1.6 × 1.5–1.7 mm, glabrous; glands 4, green to red, slightly concave, elliptic, oblong, or subcircular, 0.3–0.5 × 0.4–0.6 mm; appendages white or pink, semilunate, fringing edge of gland, sometimes rudimentary, (0–)0.1–0.5(–0.7) × 0.5–0.8 mm, distal margin crenate to entire. |
Staminate flowers | 5–12. |
5–16. |
Pistillate flowers | ovary pilose, styles 0.5–0.6 mm, 2-fid 1/2 length. |
ovary glabrous; styles 0.2–0.3 mm, 2-fid 1/2 length. |
Capsules | broadly ovoid to subglobose, 1.4–1.8 mm diam., pilose; columella 1.1–1.4 mm. |
broadly ovoid, 2–2.1 × 2.3–2.5 mm, glabrous; columella 1.5–2 mm. |
Seeds | gray to light brown, ovoid, 4-angled in cross section, 0.9–1.1 × 0.5–0.6 mm, rugose with 2–5 irregular transverse ridges that sometimes pass through abaxial keel. |
ashy white, plumply ovoid, terete to bluntly subangled in cross section, 1.5–1.9 × 1–1.2 mm, smooth or minutely pitted, with smooth brown line from top to bottom on adaxial side. |
Cyathia | solitary at distal nodes; peduncle 0.7–3.6 mm. |
solitary or in small, cymose clusters at distal nodes; peduncle 0.5–3 mm. |
Euphorbia arizonica |
Euphorbia bombensis |
|
Phenology | Flowering and fruiting year-round in response to sufficient moisture. | Flowering and fruiting spring–fall. |
Habitat | Washes and rocky slopes, sometimes on limestone, desert scrub communities often with creosote-bush, riparian forests, mesquite woodlands, oak chaparral. | Coastal dunes and sandy habitats. |
Elevation | 100–1400 m. (300–4600 ft.) | 0–30 m. (0–100 ft.) |
Distribution |
AZ; CA; NM; TX; Mexico (Baja California, Baja California Sur, Chihuahua, Coahuila, Durango, Sonora)
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AL; FL; GA; LA; MS; NC; SC; TX; VA; Mexico; Central America; n South America (Venezuela)
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Discussion | Euphorbia arizonica is distinctive and easily recognized by its glistening, translucent hairs that appear somewhat glutinous and are most apparent on the stems. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Euphorbia bombensis is similar and closely related to E. cumulicola, E. geyeri, and E. polygonifolia. It differs notably from E. polygonifolia in its smaller, plumply ovoid seeds. L. C. Wheeler (1941) suggested that where E. bombensis and E. polygonifolia are sympatric, E. bombensis grows farther away from the shore. Euphorbia bombensis is usually distinguished from E. cumulicola by the latter's smaller, isomorphic leaves that lack any fleshiness, smaller seeds, and diffuse growth habit. Euphorbia bombensis differs from E. geyeri in its usually shorter, less conspicuous involucral gland appendages and its geographic restriction to the coastal plain. However, Wheeler pointed out that plants of E. bombensis from Texas have more or less conspicuous involucral gland appendages. Examination of specimens confirmed that E. bombensis occasionally has conspicuous involucral gland appendages, and because of this, E. bombensis and E. geyeri are difficult to distinguish in Texas. This clade of closely related, sand and dune specialists requires further study. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 260. | FNA vol. 12, p. 261. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | Chamaesyce arizonica | Chamaesyce ammannioides, C. bombensis, C. ingallsii, E. ammannioides |
Name authority | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 186. (1859) | Jacquin: Enum. Syst. Pl., 22. (1760) |
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