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Key to Euphorbia
https://fsus.ncbg.unc.edu/main.php?pg=show-key.php&keyid=40083
1 Shrubs with succulent stems; [subgenus Euphorbia, sect. Crepidaria]. | |
3 Leaves strictly opposite, oblique or inequilateral at base; branches prostrate (less usually erect); [subgenus Chamaesyce; section Anisophyllum] | |
6 Ovary and capsule subtended by a calyx-like structure; seeds without caruncles; involucral gland appendages absent; [subgenus Euphorbia; section Nummulariopsis] | |
6 Ovary and capsule not subtended by a calyx-like structure; seeds with caruncles; involucral gland appendages hornlike or absent; [subgenus Esula] |
Key to Euphorbia, Key A: subgenus Chamaesyce, section Anisophyllum, subsection Hypericifoliae {add to Key A: E. blodgettii, E. hypericifolia, E. mesembrianthemifolia, E. ophthalmica, E. serpyllifolia var. serpyllifolia}
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3 Seeds 1.0-1.3 mm long, with 3-4 (-6) transverse ridges; involucre 0.6-0.9 mm long; stems prostrate; [s. IN and c. TN westward, primarily w. of MS river] | |
3 Seeds 0.8-1.1 mm long, with 2-4 transverse ridges; involucre 0.9-1.1 mm long; stems erect to ascendant; [SC s. to FL and w. to TX in our region]. | |
4 Stipules inconspicuous, ca. 0.5 mm long; stems (at least sparsely) pilose proximally and glabrous distally; plants to 80 cm long; capsules 1.7-1.8 mm wide; seeds 1.0-1.4 mm long, with 2-3 prominent transverse ridges | |
2 Leaves absolutely entire; seeds smooth. | |
8 Seeds ashy white with a brown longitudinal line on adaxial surface, 1.1-1.4 (-1.6) mm long; leaf bases angled or rounded, with one side of the leaf base often expanded into a small rounded auricle | |
11 Seeds 0.8-1.0 mm long, light gray, the faces with 2-3 (-4) horizontal, low, blunt ridges, sometimes connected by 1-2 cross ridges; stems glabrous when young (uncommonly puberulent along 1 side of the branchlets); capsule 1.5-2.0 mm long | |
11 Seeds 1.0-1.3 mm long, dark gray, faces without ridges, though irregularly and finely wrinkled; stems puberulent when young on 1 side only; capsule 2.0-2.5 mm long. | |
14 Capsules spreading-villous, especially or solely on the angles; styles 0.2-0.3 mm long, bifid nearly to the base; seeds sharply quadrangular-angled, the faces with 3-4 transverse ridges | |
14 Capsules minutely appressed-puberulent, on the entire surface (though sometimes primarily on the lower portion); styles 0.3-0.7 mm long, bifid only in the upper half or third; seeds quadrangular but not angled, the faces with inconspicuous transverse ridges or nearly smooth. | |
15 Involucre cleft on 1 side half its length; leaves mostly obovate, 1.5-2× as long as wide; styles 0.5-0.7 mm long, filiform; seed faces nearly smooth; adventitious roots formed at middle nodes along the stem | |
15 Involucre cleft on 1 side a fourth to a third its length; leaves mostly oblong, 2-3× as long as wide; styles 0.3-0.4 mm long, clavate; seed faces transversely ridged; adventitious roots not formed |
Key to Euphorbia, Key B: subgenus Chamaesyce, section Poinsettia
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2 Leaf undersurface hairs stiff and distinctly widened towards their bases; capsules 4.0-4.8 mm wide; seeds angular in cross section, unevenly tuberculate |
2 Leaf undersurface hairs soft and little or not thickened towards their bases; capsules 3.5-4.0 mm wide; seeds rounded in cross section, evenly tuberculate |
3 Cyathial gland with a circular opening; bracteal leaves wholly green or green and paler at base (sometimes purple-spotted); seeds angular, with a small caruncle and pronounced longitudinal dorsal ridge, but lacking a distinct transverse tubercular ridge near the middle |
3 Cyathial gland 2-lipped, the opening elliptical and elongate; bracteal leaves wholly green, purple, white, pink, or red, or green or purplish towards the tip and white, pink, or red at the base; seeds cylindrical, lacking both a caruncle and longitudinal dorsal ridge, but with a distinct transverse tubercular ridge near the middle. |
4 Annual herbs from spreading taproots; leaf blades 4-40 mm wide; bracteal leaves usually green with white, pink, or red at base, or some or all bracts wholly white, pink, red, or green; capsules green at maturity; involucral glands 1; [widespread in our region] |
4 Perennial herbs with thick, woody taproots; bracteal leaves usually purplish green (or with pink at base); capsules purplish at maturity; involucral glands 3-5; [s. FL] |
Key to Euphorbia, Key C: subgenus Chamaesyce, section Alectoroctonum
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1 Upper stem leaves and/or dichasial bracts with white margins or entirely white. | |
2 Cyathial bracts glabrous, often entirely white (less commonly only white along margins) | |
2 Cyathial bracts densely pilose, with conspicuous white margins. | |
1 Upper stem leaves and bracteal leaves entirely green, not whitened. | |
6 Leaves broad (ovate, oblanceolate, elliptic, or lanceolate), < 5.5× as long as wide; leaf blades slightly revolute or planar; glands green. | |
7 Involucral glands 5; leaf adaxial (upper) surface usually glabrous (besides ciliate margins in E. apocynifolia); leaf bases cuneate to rounded. | |
9 Plants (2-) 4-9 (-13) dm tall; aerial stems multiple, (1-) 3-10 stems from a crown, each (1.2-) 2.5-5 (-7) mm in diameter at the base; leaves ascending, leathery, sessile; primary bracts smaller than stem leaves; petaloid appendages oblong or spatulate, 2.5-4.4 mm long; seeds 2.6-3.2 mm long; [NH and MA west to s. ON, MI, WI, MN, and NE, south to se.VA, c. NC, n. GA, s. AL, and e. TX] | |
9 Plants 3.5-6.5 dm tall; aerial stems 1 (-3) from a crown, each 1.0-2.2 mm in diameter at the base; leaves usually reflexed, thin, petiolate or subpetiolate; primary bracts similar to stem leaves in size; petaloid appendages orbicular or oval, 0.9-2.2 mm long; seeds 1.8-2.3 mm long; [c. MD, VA, and c. and sw. TN, south to Panhandle FL and s. MS] | |
11 Leaf margins not ciliate (except some marginal hairs in E. curtisii); cyathia 2.0-3.4 mm wide (across the appendages), green or maroon; leaves slightly to strongly fleshy, 0.7-20× as long as wide, often very variable in shape, even on the same plant; [of more or less xeric sandhill woodlands with acidic, sandy soils]. | |
12 Stems 1-4 (-9) per crown, erect to strongly ascending; leaves alternate, opposite, or in whorls of 3 (at least some alternate on a plant), less fleshy, green to blue-green, without a red margin (or with a very narrow, slightly red-hyaline, but not thickened margin in E. exserta); branching alternate below the inflorescence (rarely dichotomous or trichotomous), the branches typically unequal. | |
13 Cyathia and capsules green; petaloid appendages white or pink; leaves thin-textured, green, finely pubescent with appressed white hairs (0.1-0.3 mm long) on the lower surface and margins (visible at 10× or greater); branching primarily alternate; leaves primarily alternate (typically opposite or 3-whorled below the inflorescence); cyathia unisexual, plants usually unisexual (dioecious) | |
Key to Euphorbia, Key D: subgenus Euphorbia, section Nummulariopsis
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Key to Euphorbia, Key E: subgenus Esula
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3 Leaf margins serrulate, the teeth pointed; terminal pleiochasial branches (rays) usually 5 and conspicuously radiating from above; capsules 2.5-4 mm long; seeds 1.6-2.2 mm long [uncommon non-native of disturbed areas in e. US] | |
4 Plants perennial, with thickened woody taproots; stems villous (often densely so, especially on inflorescence branches); leaves to 25 mm wide; [non-native waif] | |
4 Plants annual, rarely biennial, with thin herbaceous to only partially woody taproots; stems glabrous (or occasionally pilose in E. platyphyllos); leaves to 11 mm wide; [natives and waifs]. | |
6 Seeds smooth or very obscurely reticulate, 1.7-2.5 mm long; cyathia with the involucre 1.2-1.5 mm long; involucral bracts typically red; dichasial bracts cordate-clasping | |
6 Seeds distinctly alveolate, 1.3-1.8 mm long; cyathia with the involucre 0.6-0.9 mm long; involucral bracts typically yellow; dichasial bracts rounded to subcordate | |
1 Principal stem leaves entire. | |
7 Stem leaves opposite, decussate (each succeeding pair turned by 90 degrees); seeds 4-6 mm long; [subgenus Esula, section Lathyris] | |
8 Stem leaves oblanceolate, obovate, elliptic, spatulate, or oblong, 10-100 (-150) mm long, (3-)5-30 mm wide, averaging 1-5× as long as wide. | |
10 Principal stem leaves elliptic to oblong, (50-) 70-100 cm long; rhizomatous perennial to 1 m tall; seeds smooth, 3-5 mm long; rays of the umbel usually 5-8; [subgenus Esula, section Helioscopia] | |
10 Principal stem leaves oblanceolate to obovate, 10-20 mm long; annual, biennial, or perennial by basal offshoots, to 0.4 m tall; seeds pitted, 1.3-2.0 mm long; rays of the umbel 3 (-5). | |
11 Seeds pitted only on one face, the inner face furrowed; [subgenus Esula, section Tithymalus] | |
12 Seeds either finely pitted with numerous, evenly distributed, isodiametric pits, or tuberculate; glands of the cyathia crescent-shaped, the horns slender, elongate, and caudate; [subgenus Esula, section Tithymalus]. | |
13 Seeds finely pitted with numerous, evenly distributed, isodiametric pits. | |
15 Petioles 2-5 mm long; capsules subglobose, 2-2.5 mm long; seeds with scattered, deep and broad pits; [TX] | |
14 Dichasial bracts usually distinct, occasionally subconnate basally. | |
17 Biennial or occasionally annual herbs; petioles of lower stem leaves 5-10 mm long; leaf blades usually oblanceolate to obovate, rarely ovate, 3-10 mm wide (at least some blades more than 5 mm wide); capsules 2.5-3.2 mm long. | |
17 Annual herbs; petioles of lower stem leaves 0-2 mm long; leaf blades linear to oblanceolate, spatulate-cuneate, or slightly lanceolate, 0.5-5 mm wide; capsules 1.8-2.4 mm long. | |
18 Seeds white to gray, 1.4-1.7 × 1-1.6 mm, with pits scattered over entire surface. | |
19 Leaf blades oblanceolate, 3-5 mm wide; seeds ovoid, 1.6-1.7 × 1.4-1.6 mm; [granitic outcrops, GA]. | |
19 Leaf blades linear to slightly lanceolate or linear-oblanceolate, 0.5-2.5 mm wide; seeds ellipsoid, 1.4-1.7 × 1.0-1.3 mm; [sandy soils, TX Coastal Plain]. | |
20 Stems 6-13 cm tall; leaf blades linear to slightly lanceolate, apices acute; dichasial bracts broadly ovate-lanceolate, bases rounded; seeds 1.4-1.5 × 1-1.1 mm, the surfaces with irregular, not obviously concave depressions; [Jim Hogg, Kenedy counties, TX] |