Euphorbia capitellata |
Euphorbia pubentissima |
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capitate sandmat, head sandmat, head spurge |
false flowering spurge, southeastern flowering spurge |
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Habit | Herbs, annual or perennial, with slender to thick and woody rootstock. | Herbs, perennial, with spreading rootstock. |
Stems | usually ascending (but ranging from decumbent to erect), 15–50 cm, glabrous, strigillose, or pilose. |
erect, usually unbranched, occasionally few branched distally, solitary or few, previous year's dead stems not persistent, 30–65 cm, usually glabrous, rarely villous. |
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; stipules 1 mm; petiole (0–)1–2(–10) mm, glabrous or densely villous; blade lanceolate, lance-ovate, elliptic, or obovate, 40–68 × 6–18 mm, often reflexed, base cuneate to rounded, margins entire, apex usually rounded, sometimes broadly acute, abaxial surface glabrous or villous, adaxial surface usually glabrous, rarely sparsely villous; venation occasionally obscure on small leaves, midvein conspicuous. |
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 or hemispheric, 1.3–1.7 × 1.8–2.2 mm, glabrous or villous; glands 5 (7–10 on central cyathium), green, reniform or broadly elliptic, 0.3–0.5 × 0.5–0.8 mm; appendages white, orbiculate or narrowly flabellate, 1–2.2 × 1.5 mm, entire. |
Staminate flowers | 25–40. |
20–25. |
Pistillate flowers | ovary glabrous or pilose; styles 0.4–0.6 mm, 2-fid entire length. |
ovary glabrous or sparsely villous; styles 0.6–1.1 mm, 2-fid 1/2 length. |
Capsules | ovoid to oblate, 1.3–1.9 × 1.4–2.1 mm, glabrous or pilose; columella 1.1–1.7 mm. |
globose, 2–2.4 × 3.3–4.8 mm, glabrous or sparsely villous; columella 1.8–2.1 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. |
light gray, ovoid, 2.2–2.4 × 1.6–1.8 mm, with shallow depressions; caruncle absent. |
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 terminal pleiochasia; peduncle 1–5 mm (or 15–40 mm on early flowering individuals), usually glabrous, occasionally sparsely villous. |
2n | = 14. |
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Euphorbia capitellata |
Euphorbia pubentissima |
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Phenology | Flowering and fruiting year-round in response to sufficient moisture. | Flowering and fruiting spring–fall. |
Habitat | Gravelly washes, rocky slopes, basaltic talus, disturbed roadsides, primarily desert scrub, desert grasslands, riparian forests, rarely oak-juniper woodlands. | Open fields, cliffs, woods, floodplains. |
Elevation | 600–1600 m. (2000–5200 ft.) | 0–900 m. (0–3000 ft.) |
Distribution |
AZ; NM; TX; Mexico (Baja California, Baja California Sur, Chihuahua, Coahuila, Sinaloa, Sonora)
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AL; FL; GA; LA; MD; MS; NC; SC; TN; VA; WV
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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.) |
The taxonomic history of Euphorbia pubentissima is complex. The species has been included within a very broadly defined E. corollata in the past. Therefore, its geographic distribution appears significantly more wide-ranging in some treatments. The framework established by M. J. Huft (1979) and later by K. R. Park (1998) is followed here. Euphorbia pubentissima is recognized as a variable species restricted to the southeastern United States. The species can be distinguished from E. corollata by its shorter involucral gland appendages and smaller seeds. Euphorbia paniculata Elliott, which sometimes is applied to E. pubentissima, is an illegitimate name (a later homonym of Euphorbia paniculata Desfontaines). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 262. | FNA vol. 12, p. 250. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > sect. Alectoroctonum |
Sibling taxa | ||
Synonyms | Chamaesyce capitellata, C. pycnanthema, E. pycnanthema | E. apocynifolia, E. corollata var. paniculata, E. corollata var. zinniiflora, E. zinniiflora, Tithymalopsis apocynifolia, T. paniculata, T. zinniiflora |
Name authority | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 188. (1859) | Michaux: Fl. Bor.-Amer. 2: 212. (1803) |
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