Euphorbia dentata |
Euphorbia sect. Poinsettia |
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green poinsettia, tooth poinsettia, tooth spurge |
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Habit | Herbs, annual, with taproot. | Herbs, annual or perennial [rarely shrubs or small trees], with taproot or tuberous rootstock. | ||||||||||||||||||||||||||||||||||||
Stems | erect or ascending, 15–60 cm, both pilose and inconspicuously strigillose; branches usually ± straight, occasionally proximal branches arcuate. |
erect or ascending, branched, terete, glabrous or hairy. |
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Leaves | 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. |
opposite or alternate; stipules usually present, occasionally absent, at base of petiole; petiole present, glabrous or hairy; blade monomorphic (occasionally polymorphic in E. cyathophora and E. heterophylla), base symmetric, margins entire or toothed, flat to revolute, surfaces glabrous or variously hairy; venation pinnate, midvein often prominent. |
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Involucre | 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. |
± actinomorphic, not spurred; glands 1–3 (sometimes 4–5 in E. eriantha, E. exstipulata, and E. radians), sessile or stipitate, shallowly cupped to deeply concave; appendages absent or petaloid (E. bifurcata, E. eriantha, and E. exstipulata). |
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Staminate flowers | 8–10. |
3–25. |
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Pistillate flowers | ovary glabrous, styles 1.2 mm, 2-fid 1/2 to nearly entire length. |
ovary glabrous or hairy; styles distinct, occasionally appearing connate at base, unbranched or 2-fid. |
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Capsules | depressed-globose, 2.5–2.8 × 3.5–4 mm, 3-lobed, glabrous; columella 1.8–2.1 mm. |
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Seeds | 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. |
caruncle present or absent. |
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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). |
arrangement: terminal monochasia, dichasia, or condensed pleiochasia with 1–3 primary branches; individual pleiochasial branches unbranched or few-branched at 1 or more successive nodes; bracts subtending pleiochasia (pleiochasial bracts) opposite or whorled, usually wholly green or with paler green, white, pink, or red at base, sometimes wholly white, pink, or red, similar in shape and size to distal leaves or distinctly different, those on branches and subtending cyathia (dichasial and subcyathial bracts) opposite, distinct; additional cymose branches occasionally present in axils of distal leaves, but alternately arranged and without whorled bracts. |
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Cyathia | peduncle 0.7–1 mm. |
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x | = 7. |
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2n | = 28. |
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Euphorbia dentata |
Euphorbia sect. Poinsettia |
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Phenology | Flowering and fruiting spring–fall. | |||||||||||||||||||||||||||||||||||||
Habitat | Bottomland forests, stream and river banks, bluffs, prairies, glades, fallow fields, roadsides, railroad cinders, open disturbed areas. | |||||||||||||||||||||||||||||||||||||
Elevation | 0–1000 m. (0–3300 ft.) | |||||||||||||||||||||||||||||||||||||
Distribution |
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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North America; Mexico; Central America; South America; West Indies; Eurasia; Africa; Indian Ocean Islands; Pacific Islands; Australia |
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Discussion | 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.) |
Species ca. 30 (10 in the flora). Section Poinsettia belongs to Euphorbia subg. Chamaesyce (Gray) Reichenbach. An expanded sect. Poinsettia is recognized here to include three species that have previously often been included in sect. Alectoroctonum (Schlechtendal) Baillon (E. bifurcata, E. eriantha, and E. exstipulata). These three species differ from the so-called core Poinsettia by the presence of involucral gland appendages, but they possess the shallowly to deeply concave involucral glands and toothed leaves that are generally diagnostic for the broader section. Molecular phylogenetic analyses clearly unite these three species with the other members of sect. Poinsettia and not with sect. Alectoroctonum (Y. Yang et al. 2012). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 12, p. 321. | FNA vol. 12, p. 317. | ||||||||||||||||||||||||||||||||||||
Parent taxa | Euphorbiaceae > Euphorbia > sect. Poinsettia | Euphorbiaceae > Euphorbia | ||||||||||||||||||||||||||||||||||||
Sibling taxa | ||||||||||||||||||||||||||||||||||||||
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Synonyms | Poinsettia dentata | Poinsettia | ||||||||||||||||||||||||||||||||||||
Name authority | Michaux: Fl. Bor.-Amer. 2: 211. (1803) | (Graham) Baillon: Étude Euphorb., 284. (1858) | ||||||||||||||||||||||||||||||||||||
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