Euphorbia discoidalis |
Euphorbia serrula |
|
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summer spurge |
sawtooth sandmat |
|
Habit | Herbs, perennial, with spreading rootstock. | Herbs, annual, with slender taproot. |
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 or ascending, 5–20 cm, usually pilose to villous, rarely glabrate. |
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 usually distinct, rarely connate at base, triangular or laciniate into subulate segments, 1–1.8 mm, glabrous; petiole 0.3–0.8 mm, glabrous or villous; blade oblong, ovate, or elliptic, sometimes falcate, 3–11 × 2–5 mm, base asymmetric, rounded to hemicordate, margins sharply serrate to serrulate, usually with conspicuous teeth at base of leaf, apex usually obtuse, rarely acute, surfaces frequently with red blotch in center, not papillate, sparsely pilose to glabrate; 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. |
obconic, 0.8–1.1 × 0.8–1 mm, glabrous; glands 4, greenish yellow, usually reniform to elliptic, rarely circular, 0.1 × 0.1–0.2 mm; appendages usually white, rarely light pink, orbiculate, 0.1–0.3 × 0.2–0.4 mm, distal margin entire or crenulate. |
Staminate flowers | 20–25. |
7–15. |
Pistillate flowers | ovary glabrous or sparsely strigose; styles 0.5–1.1 mm, 2-fid at apex to 1/2 length. |
ovary glabrous; styles 0.3–0.5 mm, 2-fid 1/2 length. |
Capsules | globose, 1.8–3 × 2.5–4.8 mm, glabrous or sparsely strigose; columella 2.3–2.5 mm. |
oblate, cocci not elongated nor terminating in empty portion, 2–2.6 × 3.2–3.7 mm, glabrous; columella 1.7–2.1 mm. |
Seeds | light gray, ovoid, 2 × 1.2–1.3 mm, smooth or with few, very shallow depressions; caruncle absent. |
white to light brown, broadly ellipsoid to ovoid, 3–4-angled in cross section, 1.5–1.8 × 1.1–1.3(–1.5) mm, smooth to minutely rugulose or with scattered small depressions. |
Cyathia | in terminal pleiochasia; peduncle 5–15 mm, filiform, glabrous or very sparsely puberulent to sericeous. |
solitary at distal nodes; peduncle 0.4–1.8(–2.3) mm. |
Euphorbia discoidalis |
Euphorbia serrula |
|
Phenology | Flowering and fruiting late spring–fall. | Flowering and fruiting spring–fall. |
Habitat | Sand hills, pine savannas, woodland borders, open fields with sandy soils. | Desert scrub, with creosote bush, grasslands with mesquite and yucca, rarely in ponderosa pine woodlands, often sandy substrates. |
Elevation | 0–150 m. (0–500 ft.) | 300–1900 m. (1000–6200 ft.) |
Distribution |
AL; FL; GA; LA; MS; TX
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AZ; NM; TX; Mexico
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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.) |
In Mexico, Euphorbia serrula is found from Chihuahua and Coahuila south to Puebla. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 245. | FNA vol. 12, p. 288. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Alectoroctonum | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | Tithymalopsis discoidalis | Chamaesyce serrula |
Name authority | Chapman: Fl. South. U.S., 401. (1860) | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 188. (1859) |
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