Euphorbia capitellata |
Euphorbia antisyphilitica |
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capitate sandmat, head sandmat, head spurge |
candelilla, wax plant |
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Habit | Herbs, annual or perennial, with slender to thick and woody rootstock. | Shrubs, with much-branched, fleshy rootstock. |
Stems | usually ascending (but ranging from decumbent to erect), 15–50 cm, glabrous, strigillose, or pilose. |
erect, few branched, 25–50(–100) cm, glabrous or puberulent, pencil-like, in age covered with flaky, exfoliating layer of wax. |
Leaves | opposite; stipules distinct, filiform or divided into 2–3 subulate-filiform segments, without dark, circular glands at base, 0.6–1.5 mm, pilose; petioles 0.6–1.3 mm, glabrous, pilose, or strigillose; blade ovate to narrowly ovate, 4–19 × 2–8 mm, base asymmetric, one side strongly cordate, other side rounded to slightly cordate, margins entire or serrulate (commonly nearly entire with few scattered teeth, often slightly thickened), apex acute, surfaces often with red spot in center, glabrous, pilose, or strigillose; weakly 3-veined from base, usually only midvein conspicuous. |
alternate usually caducous, sometimes persisting; stipules 0.4–0.5 mm; petiole absent; blade ovate to deltate-subulate, 2.5–4 × 1 mm, thick, fleshy, base usually rounded and swollen, rarely cuneate, margins entire, apex acute, surfaces puberulent, adaxial sometimes canescent; venation inconspicuous. |
Involucre | narrowly obconic to narrowly campanulate, 0.8–1.6 × 0.7–1.3 mm, glabrous or pilose; glands 4, yellow-green to pink or maroon, circular to oblong, 0.2–0.4 × 0.2–0.5 mm; appendages white to light pink, oblong to reniform or flabellate, 0.2–1.1 × 0.5–1.7 mm, surfaces glabrous, distal margin entire. |
campanulate, 1.6–2.2 × 1.6–1.9 mm, puberulent to canescent; glands 5, pinkish, narrowly oblong to reniform, 0.3–0.4 × 0.8–1 mm; appendages white to pink, ovate, oblong, or transversely oblong, 1.3–2.5 × 1.4–2.5 mm, usually erose, rarely entire. |
Staminate flowers | 25–40. |
50–70. |
Pistillate flowers | ovary glabrous or pilose; styles 0.4–0.6 mm, 2-fid entire length. |
ovary glabrous; styles 0.9–1.1 mm, 2-fid nearly entire length. |
Capsules | ovoid to oblate, 1.3–1.9 × 1.4–2.1 mm, glabrous or pilose; columella 1.1–1.7 mm. |
oblong to ovoid, 3.9–4.2 × 3.6–3.9 mm, glabrous; columella 3.1–3.3 mm. |
Seeds | pink to pinkish gray, narrowly ovoid to narrowly ovoid-oblong, 4-angled or weakly 3-angled in cross section, 0.9–1.5 × 0.5–0.7 mm, irregularly dimpled, sometimes also with faint transverse ridges that do not pass through abaxial keel. |
whitish gray, narrowly ovoid, 2.4–3.1 × 1.4–1.6 mm, irregularly rugose-tuberculate; caruncle crescent-shaped, 0.3–0.6 × 0.6–0.8 mm. |
Cyathia | in dense, terminal capitate glomerules, with reduced, bractlike leaves subtending cyathia, at tips of main stems and short, leafy, axillary branches; peduncle 0.1–1.2 mm. |
in axillary congested cymes, near branch tips or solitary at distal nodes; peduncle 0–1 mm, lanulose. |
2n | = 14. |
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Euphorbia capitellata |
Euphorbia antisyphilitica |
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Phenology | Flowering and fruiting year-round in response to sufficient moisture. | Flowering and fruiting year-round in response to sufficient rainfall. |
Habitat | Gravelly washes, rocky slopes, basaltic talus, disturbed roadsides, primarily desert scrub, desert grasslands, riparian forests, rarely oak-juniper woodlands. | Desert scrub, frequently on limestone substrates. |
Elevation | 600–1600 m. (2000–5200 ft.) | 100–1200 m. (300–3900 ft.) |
Distribution |
AZ; NM; TX; Mexico (Baja California, Baja California Sur, Chihuahua, Coahuila, Sinaloa, Sonora)
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NM; TX; Mexico
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Discussion | Euphorbia capitellata is a characteristic herb in the Sonoran Desert of southern Arizona, ranging east to extreme southwestern Texas. During peak flowering, plants are attractive due to the dense clusters of cyathia with well-developed involucral gland appendages. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Euphorbia antisyphilitica is the only pencil-stemmed species of Euphorbia occurring in the flora area. The species is characteristic of the Chihuahuan Desert scrub of Mexico from Chihuahua and Coahuila south to Hidalgo and Querétaro, and barely enters into the United States in southern New Mexico (Doña Ana and Lincoln counties) and southwest (Brewster, Hudspeth, Presidio, and Terrell counties) and south (Starr and Webb counties) Texas. The stems are covered in a conspicuous coat of exfoliating wax, and the plants historically have been harvested for this product, although the practice is much less prevalent now. The specific epithet refers to its traditional medicinal use in treating sexually transmitted infections. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 262. | FNA vol. 12, p. 243. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > sect. Alectoroctonum |
Sibling taxa | ||
Synonyms | Chamaesyce capitellata, C. pycnanthema, E. pycnanthema | |
Name authority | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 188. (1859) | Zuccarini: Flora 15(2, Beibl.): 58. (1832) |
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