Euphorbia discoidalis |
Euphorbia bombensis |
|
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summer spurge |
Dixie sandmat, southern seaside spurge |
|
Habit | Herbs, perennial, with spreading rootstock. | Herbs, usually annual, rarely perennial, with 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 slightly ascending, 10–40 cm, glabrous. |
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, linear-subulate, usually divided into 3 linear segments, 1–2 mm, glabrous; petiole 1–2 mm, glabrous; blade oblong or elliptic-oblong, 4–15 × 2–3 mm, base asymmetric to nearly symmetric, obtuse, margins entire, apex acute to mucronate, surfaces green to reddish flushed, glabrous; 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-campanulate, 1.2–1.6 × 1.5–1.7 mm, glabrous; glands 4, green to red, slightly concave, elliptic, oblong, or subcircular, 0.3–0.5 × 0.4–0.6 mm; appendages white or pink, semilunate, fringing edge of gland, sometimes rudimentary, (0–)0.1–0.5(–0.7) × 0.5–0.8 mm, distal margin crenate to entire. |
Staminate flowers | 20–25. |
5–16. |
Pistillate flowers | ovary glabrous or sparsely strigose; styles 0.5–1.1 mm, 2-fid at apex to 1/2 length. |
ovary glabrous; styles 0.2–0.3 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. |
broadly ovoid, 2–2.1 × 2.3–2.5 mm, glabrous; columella 1.5–2 mm. |
Seeds | light gray, ovoid, 2 × 1.2–1.3 mm, smooth or with few, very shallow depressions; caruncle absent. |
ashy white, plumply ovoid, terete to bluntly subangled in cross section, 1.5–1.9 × 1–1.2 mm, smooth or minutely pitted, with smooth brown line from top to bottom on adaxial side. |
Cyathia | in terminal pleiochasia; peduncle 5–15 mm, filiform, glabrous or very sparsely puberulent to sericeous. |
solitary or in small, cymose clusters at distal nodes; peduncle 0.5–3 mm. |
Euphorbia discoidalis |
Euphorbia bombensis |
|
Phenology | Flowering and fruiting late spring–fall. | Flowering and fruiting spring–fall. |
Habitat | Sand hills, pine savannas, woodland borders, open fields with sandy soils. | Coastal dunes and sandy habitats. |
Elevation | 0–150 m. (0–500 ft.) | 0–30 m. (0–100 ft.) |
Distribution |
AL; FL; GA; LA; MS; TX
|
AL; FL; GA; LA; MS; NC; SC; TX; VA; Mexico; Central America; n South America (Venezuela)
|
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 bombensis is similar and closely related to E. cumulicola, E. geyeri, and E. polygonifolia. It differs notably from E. polygonifolia in its smaller, plumply ovoid seeds. L. C. Wheeler (1941) suggested that where E. bombensis and E. polygonifolia are sympatric, E. bombensis grows farther away from the shore. Euphorbia bombensis is usually distinguished from E. cumulicola by the latter's smaller, isomorphic leaves that lack any fleshiness, smaller seeds, and diffuse growth habit. Euphorbia bombensis differs from E. geyeri in its usually shorter, less conspicuous involucral gland appendages and its geographic restriction to the coastal plain. However, Wheeler pointed out that plants of E. bombensis from Texas have more or less conspicuous involucral gland appendages. Examination of specimens confirmed that E. bombensis occasionally has conspicuous involucral gland appendages, and because of this, E. bombensis and E. geyeri are difficult to distinguish in Texas. This clade of closely related, sand and dune specialists requires further study. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 245. | FNA vol. 12, p. 261. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Alectoroctonum | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | Tithymalopsis discoidalis | Chamaesyce ammannioides, C. bombensis, C. ingallsii, E. ammannioides |
Name authority | Chapman: Fl. South. U.S., 401. (1860) | Jacquin: Enum. Syst. Pl., 22. (1760) |
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