Euphorbia polygonifolia |
Euphorbia dentata |
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dune spurge, euphorbe à feuilles de renouée, seaside sandmat, seaside spurge |
green poinsettia, tooth poinsettia, tooth spurge |
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Habit | Herbs, annual, with taproot. | Herbs, annual, with taproot. |
Stems | usually prostrate, occasionally ascending, 5–30 cm, glabrous. |
erect or ascending, 15–60 cm, both pilose and inconspicuously strigillose; branches usually ± straight, occasionally proximal branches arcuate. |
Leaves | opposite; stipules usually distinct, occasionally connate basally (distal portion of stem), triangular-subulate, entire or divided, 0.8–1.5 mm, glabrous; petiole 1–3 mm, glabrous; blade oblong, linear-oblong, or linear-lanceolate, 5–16 × 2–4 mm, base slightly asymmetric, obtuse or subcordate, margins entire, apex obtuse, often mucronulate, surfaces uniformly green or reddish tinged, glabrous; venation obscure. |
usually opposite, occasionally alternate at distal nodes; petiole 5–20 mm, pilose; blade 30–70 × 4–35 mm, narrowly lanceolate to suborbiculate, usually broadest below middle, base usually acute to subobtuse, rarely subtruncate, margins coarsely crenate-dentate or doubly crenate, strigillose, flat to slightly revolute, apex broadly acute, abaxial surface long pilose with weak, filiform hairs, adaxial surface sparsely pilose to glabrate; venation pinnate, midvein prominent. |
Involucre | obconic-campanulate, 1.2–1.7 × 1–1.4 mm, glabrous; glands 4, occasionally rudimentary, green-yellow to tan or orange-tinged, occasionally shortly stipitate, usually broadly oval to subcircular, sometimes figure eight-shaped, shallowly cupped, 0.1–0.3 × 0.2–0.4 mm; appendages absent or rudimentary. |
campanulate, 3.8 × 1.8 mm, glabrous; involucral lobes divided into several linear, smooth lobes; glands (1–)2, green, sessile and broadly attached, 0.7–0.9 × 0.9–1.2 mm, opening oblong, glabrous; appendages absent. |
Staminate flowers | 5–14. |
8–10. |
Pistillate flowers | ovary glabrous; styles 0.7–1 mm, 2-fid 1/2 length. |
ovary glabrous, styles 1.2 mm, 2-fid 1/2 to nearly entire length. |
Capsules | broadly ovoid, 3–3.5(–4) × (2–)2.4–3 mm, glabrous; columella 2–3 mm. |
depressed-globose, 2.5–2.8 × 3.5–4 mm, 3-lobed, glabrous; columella 1.8–2.1 mm. |
Seeds | ashy white, wedge-shaped to slightly ovoid, weakly dorsiventrally compressed and elliptic-terete to bluntly subangled in cross section, back strongly rounded, face slightly rounded, (2–)2.2–2.8 × 1.6–1.9 mm, smooth or minutely pitted, with smooth brown line from top to bottom on adaxial side. |
pale gray to black, ovoid, rounded in cross section, 2.1–2.7 × 1.7–2.1 mm, evenly minute-tuberculate; caruncle 0.4–0.6 mm. |
Cyathia | solitary or in small, cymose clusters at distal nodes; peduncle 0.5–5 mm. |
peduncle 0.7–1 mm. |
Cyathial | arrangement: terminal pleiochasial branches usually 3, occasionally reduced to congested cyme, 1–2-branched; pleiochasial bracts 2–4, often whorled, wholly green or paler green, white, or mauve at base, similar in shape and size to distal leaves or slightly narrower; dichasial bracts similar in shape to distal leaves but smaller (often highly reduced). |
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2n | = 28. |
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Euphorbia polygonifolia |
Euphorbia dentata |
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Phenology | Flowering and fruiting early summer–fall. | Flowering and fruiting spring–fall. |
Habitat | Sandy maritime and freshwater beaches and foredunes. | Bottomland forests, stream and river banks, bluffs, prairies, glades, fallow fields, roadsides, railroad cinders, open disturbed areas. |
Elevation | 0–200 m. (0–700 ft.) | 0–1000 m. (0–3300 ft.) |
Distribution |
CT; DE; FL; GA; IL; IN; MA; MD; ME; MI; NC; NH; NJ; NY; OH; PA; RI; SC; VA; WI; NB; NS; ON; PE; QC
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AL; AR; GA; IA; IL; IN; KS; KY; LA; MD; MI; MO; MS; NC; NE; OH; OK; PA; SC; TN; TX; VA; WV; ON; Mexico (Chihuahua, Coahuila, Nuevo León, Tamaulipas)
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Discussion | Euphorbia polygonifolia is native to coastal beaches and dunes along the Atlantic Ocean from the maritime provinces of Canada south to northern Florida. The species also occurs disjunctly along the shores of the North American Great Lakes. Euphorbia polygonifolia was native to Quebec but is now considered extirpated from the province. It has apparently been introduced in Europe, but it is unclear if it has persisted there (L. C. Wheeler 1941). Immature individuals of this species can be somewhat difficult to distinguish from E. bombensis where their ranges overlap (Virginia to northern Florida). Where they occur together, E. polygonifolia tends to be a pioneer species on the upper beach and foredune front, whereas E. bombensis tends to inhabit areas behind the foredune (R. D. Porcher and D. A. Rayner 2002). Euphorbia polygonifolia can be distinguished also by its larger capsules and larger, wedge-shaped to slightly ovoid seeds. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Euphorbia dentata is native from northern Mexico and the south central United States north and east through the Ohio River Valley. Scattered occurrences in the southeastern United States likely represent adventive populations. Reports of E. dentata as a noxious weed (from the United States and the Old World) should most likely be attributed to introductions of E. davidii. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 284. | FNA vol. 12, p. 321. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > sect. Poinsettia |
Sibling taxa | ||
Synonyms | Chamaesyce polygonifolia | Poinsettia dentata |
Name authority | Linnaeus: Sp. Pl. 1: 455. (1753) | Michaux: Fl. Bor.-Amer. 2: 211. (1803) |
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