Euphorbia discoidalis |
Euphorbia indivisa |
|
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summer spurge |
royal sandmat |
|
Habit | Herbs, perennial, with spreading rootstock. | Herbs, annual or short-lived perennial, with slender taproot to thickened and woody 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. |
prostrate, usually mat-forming, terete to slightly flattened, 40 cm, lower surface glabrous, upper surface strigillose, pilose or villous. |
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. |
opposite; stipules distinct, entire or divided into 3–4 subulate to filiform segments, 0.8–2 mm, usually pilose, rarely glabrous; petiole 0.5–1 mm, pilose to villous; blade oblong, ovate or narrowly obovate, 3–10(–12) × 2–6 mm, base strongly asymmetric, hemicordate, margins serrulate, apex obtuse to subacute, surfaces glabrous or slightly pilose; 3-veined from base, often 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. |
narrowly turbinate, 1–1.2 × 0.4–0.7 mm, pilose; glands 4, yellow to pink, unequal, proximal pair oblong or linear, 0.1 × 0.3–0.4(–0.6) mm, distal pair oblong or subcircular, 0.1 × 0.1–0.2 mm; appendages pink to reddish, unequal, on proximal glands oblique, 0.4–0.8(–1) × 0.8–1.4(–2) mm, on distal glands symmetric, 0.2–0.5 × 0.2–0.5 mm, slightly undulate to slightly crenate. |
Staminate flowers | 20–25. |
5–15. |
Pistillate flowers | ovary glabrous or sparsely strigose; styles 0.5–1.1 mm, 2-fid at apex to 1/2 length. |
ovary pilose to strigillose in parts, glabrous in other parts; styles 0.8–1.3 mm, usually unbranched, rarely 2-fid at apex, filiform. |
Capsules | globose, 1.8–3 × 2.5–4.8 mm, glabrous or sparsely strigose; columella 2.3–2.5 mm. |
ovoid-triangular, 1.2–1.5 × 1–1.4 mm, pilose to strigillose in parts, glabrous in other parts; columella 1–1.3 mm. |
Seeds | light gray, ovoid, 2 × 1.2–1.3 mm, smooth or with few, very shallow depressions; caruncle absent. |
brown to light gray, ovoid, 4-angled in cross section, 0.8–1 × 0.4–0.5 mm, with 4 or 5 deep transverse sulci alternating with low transverse ridges. |
Cyathia | in terminal pleiochasia; peduncle 5–15 mm, filiform, glabrous or very sparsely puberulent to sericeous. |
usually in small cymose clusters on congested, axillary branches; peduncle rudimentary or to 0.2 mm. |
Euphorbia discoidalis |
Euphorbia indivisa |
|
Phenology | Flowering and fruiting late spring–fall. | Flowering and fruiting summer–fall. |
Habitat | Sand hills, pine savannas, woodland borders, open fields with sandy soils. | Grasslands, oak forests, oak-mesquite woodlands, oak-juniper communities, rarely entering desert scrub. |
Elevation | 0–150 m. (0–500 ft.) | 1000–2000 m. (3300–6600 ft.) |
Distribution |
AL; FL; GA; LA; MS; TX
|
AZ; NM; TX; Mexico
|
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 indivisa is characteristic of grasslands and oak woodlands from extreme western Texas to southeastern Arizona. The species is often treated as a synonym of E. dioeca Kunth, but the two species are readily separable on the basis of their seeds. The seeds of E. indivisa possess deep transverse sulci, whereas those of E. dioeca are merely rippled or with low transverse ridges. Euphorbia dioeca is a weedy species that occurs widely throughout tropical America but has yet to be encountered within the flora area. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 245. | FNA vol. 12, p. 273. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Alectoroctonum | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | Tithymalopsis discoidalis | E. dioeca var. indivisa, Chamaesyce indivisa |
Name authority | Chapman: Fl. South. U.S., 401. (1860) | (Engelmann) Tidestrom: Proc. Biol. Soc. Wash. 48: 40. (1935) |
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