Euphorbia arizonica |
Euphorbia gracillima |
|
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Arizona sandmat, Arizona spurge |
Mexican sandmat |
|
Habit | Herbs, annual or short-lived perennial, with slender to slightly thickened taproot. | Herbs, annual, with slender taproot. |
Stems | erect to ascending, 10–30 cm, uniformly pilose with glistening hairs. |
erect to ascending, 5–25 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, subulate-filiform, entire, 0.3–0.5 mm, glabrous; petiole 0.4–0.9 mm, glabrous; blade narrowly oblong to linear, often slightly falcate, 2–15 × 0.3–0.8 mm, base symmetric to subsymmetric, rounded to attenuate, margins entire, thickened and often revolute, apex acute to obtuse, surfaces 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. |
turbinate, 0.4–0.5 × 0.4–0.6 mm, glabrous; glands 4, yellow to pink, oblong to slightly reniform, (0–)0.1–1 × 0.1–0.2 mm; appendages white to pink, ovate to oblong, 0.2–0.4 × 0.1–0.3 mm, distal margin usually entire, rarely emarginate. |
Staminate flowers | 5–12. |
5–12. |
Pistillate flowers | ovary pilose, styles 0.5–0.6 mm, 2-fid 1/2 length. |
ovary glabrous; styles 0.1–0.2 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, 1.1–1.4 mm diam., glabrous; columella 0.8–1.1 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. |
orange to tan or reddish brown, narrowly ovoid, 4-angled in cross section, 0.9–1.1 × 0.5–0.6 mm, smooth. |
Cyathia | solitary at distal nodes; peduncle 0.7–3.6 mm. |
solitary at distal nodes; peduncle 0.1–0.9 mm. |
Euphorbia arizonica |
Euphorbia gracillima |
|
Phenology | Flowering and fruiting year-round in response to sufficient moisture. | Flowering and fruiting late summer–fall. |
Habitat | Washes and rocky slopes, sometimes on limestone, desert scrub communities often with creosote-bush, riparian forests, mesquite woodlands, oak chaparral. | Rocky slopes and dry washes in desert scrub. |
Elevation | 100–1400 m. (300–4600 ft.) | 600–900 m. (2000–3000 ft.) |
Distribution |
AZ; CA; NM; TX; Mexico (Baja California, Baja California Sur, Chihuahua, Coahuila, Durango, Sonora)
|
AZ; Mexico (Chihuahua, Jalisco, Sinaloa, Sonora) |
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 gracillima occurs from south-central Arizona (Pima and Pinal counties) south through northwestern Mexico. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 260. | FNA vol. 12, p. 270. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | Chamaesyce arizonica | Chamaesyce gracillima |
Name authority | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 186. (1859) | S. Watson: Proc. Amer. Acad. Arts 21: 438. (1886) |
Web links |