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Euphorbia
See list of 19 species in this genusChamaesyce, a distinctive group of usually ± prostrate plants, is here subsumed under the large genus Euphorbia. Though Chamaesyce has been shown to be a monophyletic group, its recognition creates an artificial and paraphyletic Euphorbia (Steinmann and Porter 2002). The phylogeny of Euphorbia is complex on a worldwide scale, and its dismantling into smaller, more homogeneous genera appears to be premature based on the present knowledge. Euphorbia agraria Bieb. was reported from MA by Kartesz (1999), but the report was erroneous. Euphorbia pubentissima Michx. was reported from NH by Pease (1964; as E. corollata var. mollis Millsp.), but the collection was misidentified and is E. corollata—Pease 36700 (NEBC!). Euphorbia serpens Kunth was reported from NH by Magee and Ahles (1999), but the specimen (at NHA, image seen!) is a cultivated plant grown from seeds collected in IL. Also, Euphorbia humistrata Engelm. ex Gray was reported from NH and VT by Magee and Ahles (1999), but specimens are unknown. Reference: Wheeler (1941).
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1a. Leaves opposite throughout, the blades with inequilateral bases [Figs. 628,629]; stipules present [Fig. 629]; involucre with 4 glands that possess petaloid appendages; plants annual, with prostrate to wide-spreading stems (upright in E. nutans)
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2a. Leaf blades with entire margins [Fig. 629]; seeds 2–2.6 mm long (mostly 0.9-1 mm long in C. serpens), with ± smooth faces; glands with very small or obsolete appendages
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3a. Leaf blades broad-oblong to suborbicular, 2–7 mm long; stipules united into a white, scale-like structure that is usually fringed or lobed near apex; capsules 1–1.5 mm long
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3b. Leaf blades narrow-oblong to lanceolate-oblong [Fig. 629], 8–15 mm long; stipules distinct, usually colored similar to the stem, particularly in the basal ½ of the stipule; capsules 3–3.5 mm long
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2b. Leaf blades with serrate or partially serrate margins; seeds 0.9–1.6 mm long, with finely wrinkled or ridged faces; glands with small, but evident, appendages
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4a. Leaves and stems glabrous; faces of the seed with 2–4 prominent, transverse ridges (smooth to obscurely marked in E. serpyllifolia)
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5a. Faces of the seed with 2–4 prominent, transverse ridges; each cyathium with 1–5 stamens; involucres 0.6–0.9 mm in diameter
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5b. Faces of seed smooth or obscurely roughened or pitted; each cyathium with 5–12 (–18) stamens; involucres 0.8–1.2 mm in diameter
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4b. Leaves (at least when young) and stems pubescent [Fig. 628]; faces of the seed merely wrinkled or with 3 or 4 prominent, transverse ridges in E. prostrata
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6a. Ovary and capsule pubescent [Fig. 628]
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7a. Styles 0.3–0.4 mm long, divided in the apical ⅓ to ¼; capsules appressed-puberulent; seeds obtusely angled, usually finely wrinked with inconspicuous transverse ridges on each face
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7b. Styles 0.2–0.3 mm long, divided nearly to the base; capsules spreading-villous, at least on the angles; seeds acutely angled, with 3 or 4 prominent transverse ridges on each face
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6b. Ovary and capsule glabrous
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8a. Stems prostrate to wide-spreading, usually branched from the base, rather uniformly spreading-hirsute with hairs 0.5–1.5 mm long
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8b. Stems ascending to suberect, usually unbranched in the lower portion, puberulent on the younger portions with incurved hairs up to 0.3 mm long, the hairs sometimes confined to a longitudinal strip
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1b. Leaves of the stem alternate (opposite in E. dentata, E. ipecacuanhae, and E. lathyris), the blades with equilateral bases, those subtending the cyathiescence whorled (regularly opposite in E. dentata and E. ipecacuanhae, and sometimes opposite in E. marginata); stipules absent (present in E. marginata); involucre with 1–4 glands that lack petaloid appendages or with 5 glands that possess petaloid appendages; plants annual or perennial, with ascending to erect stems
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9a. Leaves of the stem all or mostly all opposite and dentate; cyathiescence irregularly clustered near the apex of the stem, without evident, umbel-like branches; involucre with a solitary gland (rarely more)
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9b. Leaves of the stem alternate and entire in most species, never both opposite and toothed; cyathiescence with umbel-like branches; involucre with 4 or 5 glands
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10a. Involucre with 5 (rarely 4) glands, the glands with evident, white (rarely green), petaloid appendages (the petal appendages small in E. ipecacuanhae) [Fig. 626]
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11a. Petaloid appendages 0.05–0.6 mm long, shorter than wide, usually green; stems 1.5–3 dm tall
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11b. Petaloid appendages (0.5–) 1–4.4 mm long, as long as wide or longer, usually white [Fig. 626]; stems 3–10 dm tall
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12a. Leaves of the cyathiescence white on the margin or entirely white, those of the stem with broad-ovate to elliptic or obovate-oblong blades that are acute at the apex; stems and involucres pubescent; plants annual, with stipules
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12b. Leaves of the cyathiescence green, those of the stem with linear to elliptic blades that are obtuse at the apex; stems and involucres glabrous or pubescent; plants perennial, without stipules
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10b. Involucre with 4 glands, these without petaloid appendages
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13a. Leaves of the stem opposite; seeds 4–6 mm long
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13b. Leaves of the stem alternate [Fig. 627]; seeds 1.2–2.5 mm long
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14a. Leaf blades serrulate; glands of the involucre orbicular to elliptic
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15a. Leaf blades blunt or retuse at the apex, cuneate at the base; capsules smooth on the outer surface; seeds conspicuously aereolate-patterned
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15b. Leaf blades ± acute at the apex, the upper ones broad-based; capsules verrucose on the outer surface; seeds smooth or very obscurely reticulate-patterned
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14b. Leaf blades entire; glands of the involucre crescent-shaped, the concave surface facing outwards, often narrowed to horn-like ends
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16a. Umbel-like cyathiescence with 3–5 primary branches; plants annual; involucre 1–2 mm tall
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16b. Umbel-like cyathiescence with usually 7–17 primary branches; plants perennial from rhizomes; involucre 2.5–3 mm tall
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17a. Leaf blades of the stem 1–3 ×0.1–0.3 cm [Fig. 627]; seeds 1.5–2 mm long; plants 15–40 cm tall
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17b. Leaf blades of the stem 3–8 ×0.4–0.8 cm; seeds 2–2.5 mm long; plants 30–70 (–80) cm tall
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18a. Leaf blades oblanceolate to obovate or obovate-elliptic, 7–15 (–22) mm wide, 3–5 (–6) times as long as wide, usually widest above the middle and tapering to the base, obtuse to emarginate at the apex, of relatively thinner texture; terminal cyathiescence with usually 8–17 primary branches; axillary cyathiescences usually numbering 8–20
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18b. Leaf blades linear to lanceolate, 3–10 mm wide, 6–15 times as long as wide, widest below the middle and sometimes widened and rounded at the base, acute to subacute at the apex, of relatively firmer texture; terminal cyathiescence with usually 5–9 primary branches; axillary cyathiescences usually numbering 2–12
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Each photo represents one species in this genus.