Euphorbia polycarpa |
Euphorbia mercurialina |
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smallseed sandmat |
Mercury spurge |
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Habit | Herbs, perennial, with thickened, spreading rootstock. | |
Stems | erect, unbranched or branched, solitary or few, previous year's dead stems not persistent, 20–33 cm, glabrous or villous to lanate. |
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Leaves | 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. |
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Involucre | 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. |
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Staminate flowers | 10–15. |
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Pistillate flowers | ovary glabrous; styles 0.7–1.5 mm, 2-fid at apex. |
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Capsules | depressed-globose, 2.3–3.3 × 4.4–5 mm, glabrous; columella 2.7–3 mm. |
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Seeds | tan to dark brown, ovoid, 2.2 × 1.6 mm, with shallow and coarse depressions; caruncle absent. |
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Euphorbia | polycarpa is a highly variable species distributed throughout the Baja California peninsula, eastern Sonora, and the arid southwestern United States from southwestern Arizona to southern Nevada and central California. |
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l | . |
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c | . |
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Wheeler | (1941) divided the species into seven varieties, the majority of which occur in Baja California Sur. |
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He | reported two of these for the United States: var. hirtella and var. polycarpa. |
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Variety | hirtella, as the name suggests, was applied to hairy plants. |
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However | , it is here treated as a synonym of var. polycarpa, because variation in pubescence shows no geographic segregation and ranges along a continuum from glabrous or sparsely to densely hairy, and because glabrous and hairy branches can occur on the same individual. |
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Cyathia | usually in terminal pleiochasia, rarely dichasia; peduncle 1.3–2.7 mm (to 40–70 mm for central cyathium), filiform, glabrous. |
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Euphorbia polycarpa |
Euphorbia mercurialina |
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Phenology | Flowering and fruiting spring. | |
Habitat | Dry to mesic wooded slopes and ravines. | |
Elevation | 100–600 m. (300–2000 ft.) | |
Distribution |
AZ; CA; NV; nw Mexico
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AL; GA; KY; NC; TN
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Discussion | Varieties 5 (1 in the flora). Some of the varieties occurring in Mexico are highly divergent and appear to be sufficiently distinct to merit recognition as species. However, within the flora area, Euphorbia polycarpa is relatively uniform, and the only noteworthy variation involves the size of the involucral gland appendages. In the portion of the California Floristic Province occupied by E. polycarpa (Los Angeles, Orange, western Riverside, western San Diego, and Ventura counties) the appendages are conspicuously larger than those of plants throughout the remainder of its range in the southwestern United States (0.4–1.2 versus 0.1–0.3 mm). Large-appendaged plants are also common in Baja California and correspond well with the type collection. The taxonomic significance of this variation is not clear at this time, and the small-appendaged plants may merit segregation as an infraspecific taxon. However, no formal changes are proposed, awaiting a comprehensive review of the species throughout its range. (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. 283. | FNA vol. 12, p. 249. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > sect. Alectoroctonum |
Sibling taxa | ||
Subordinate taxa | ||
Synonyms | Chamaesyce polycarpa | Tithymalopsis mercurialina |
Name authority | Bentham: Bot. Voy. Sulphur, 50. (1844) | Michaux: Fl. Bor.-Amer. 2: 212. (1803) |
Web links |