Euphorbia discoidalis |
Euphorbia mercurialina |
|
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summer spurge |
Mercury spurge |
|
Habit | Herbs, perennial, with spreading rootstock. | Herbs, perennial, with thickened, spreading rootstock. |
Stems | erect or ascending, unbranched, solitary or few, previous year's dead stems not persistent, 45–70 cm, usually densely puberulent to sericeous, rarely glabrous. |
erect, unbranched or branched, solitary or few, previous year's dead stems not persistent, 20–33 cm, glabrous or villous to lanate. |
Leaves | alternate; stipules to 0.1 mm; petiole (0–)1–2 mm (or absent), densely puberulent; blade usually linear, rarely ovate, 25–55 × 1.5–4 mm, base cuneate, margins entire, revolute, apex rounded, abaxial surface glabrous or puberulent to sericeous, adaxial surface glabrous; venation often obscure on smaller leaves, midvein conspicuous. |
alternate; stipules 0.1–0.2 mm; petiole (1–)2.5–5(–6) mm, ciliate to lanate; blade elliptic to ovate-deltate, proximal greatly reduced, scalelike, 34–55 × 20–26 mm, base rounded or cuneate, margins entire, densely ciliate, apex rounded to acute, abaxial surface sparsely pilose to villous (to lanate on midrib), adaxial surface glabrous; venation obscure, only midvein conspicuous. |
Involucre | campanulate, 1.2–1.4 × 1.2–2 mm, sparsely to densely puberulent; glands 5, green, reniform, 0.2–0.3 × 0.5–0.6 mm; appendages white, orbiculate to oblong, (0.5–)1–1.7 × 1–1.5 mm, entire. |
campanulate or hemispheric, 1.5–2.5 × 2–3 mm, glabrous; glands 5, green, elliptic-reniform, 0.5 × 2 mm; appendages white, narrowly transversely-oblong to lunate, 0.6 × 2.5 mm, slightly erose. |
Staminate flowers | 20–25. |
10–15. |
Pistillate flowers | ovary glabrous or sparsely strigose; styles 0.5–1.1 mm, 2-fid at apex to 1/2 length. |
ovary glabrous; styles 0.7–1.5 mm, 2-fid at apex. |
Capsules | globose, 1.8–3 × 2.5–4.8 mm, glabrous or sparsely strigose; columella 2.3–2.5 mm. |
depressed-globose, 2.3–3.3 × 4.4–5 mm, glabrous; columella 2.7–3 mm. |
Seeds | light gray, ovoid, 2 × 1.2–1.3 mm, smooth or with few, very shallow depressions; caruncle absent. |
tan to dark brown, ovoid, 2.2 × 1.6 mm, with shallow and coarse depressions; caruncle absent. |
Cyathia | in terminal pleiochasia; peduncle 5–15 mm, filiform, glabrous or very sparsely puberulent to sericeous. |
usually in terminal pleiochasia, rarely dichasia; peduncle 1.3–2.7 mm (to 40–70 mm for central cyathium), filiform, glabrous. |
Euphorbia discoidalis |
Euphorbia mercurialina |
|
Phenology | Flowering and fruiting late spring–fall. | Flowering and fruiting spring. |
Habitat | Sand hills, pine savannas, woodland borders, open fields with sandy soils. | Dry to mesic wooded slopes and ravines. |
Elevation | 0–150 m. (0–500 ft.) | 100–600 m. (300–2000 ft.) |
Distribution |
AL; FL; GA; LA; MS; TX
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AL; GA; KY; NC; TN
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Discussion | M. J. Huft (1979) remarked that Euphorbia discoidalis is uncommon west of Alabama and referred many narrow-leaved specimens from Louisiana and Texas to E. corollata. K. R. Park (1998) included them in an expanded E. discoidalis, and that is followed here. The western populations can be distinguished from E. corollata by their shorter involucral gland appendages and revolute leaf margins. Further study of these western populations is warranted. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Euphorbia mercurialina is restricted primarily to the Cumberland Plateau and southern Appalachians, with disjunct occurrences in south-central North Carolina in the lower Piedmont. The North Carolina plants are markedly hairier than plants elsewhere, with villous or lanate stems, petioles, and abaxial leaf midribs. Euphorbia mercurialina has been reported from Florida and Virginia in the past. The Virginia plants were apparently planted (A. S. Weakley 2010), and the Florida reports are most certainly in error. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 245. | FNA vol. 12, p. 249. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Alectoroctonum | Euphorbiaceae > Euphorbia > sect. Alectoroctonum |
Sibling taxa | ||
Synonyms | Tithymalopsis discoidalis | Tithymalopsis mercurialina |
Name authority | Chapman: Fl. South. U.S., 401. (1860) | Michaux: Fl. Bor.-Amer. 2: 212. (1803) |
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