Euphorbia discoidalis |
Euphorbia tetrapora |
|
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summer spurge |
weak spurge |
|
Habit | Herbs, perennial, with spreading rootstock. | Herbs, annual, 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. |
erect, unbranched, 7–20 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. |
petiole 1–2 mm, reduced distally; blade spatulate-cuneate, 8–10 × 4–5 mm (greatly reduced in size proximally), base cuneate, margins entire, apex rounded to emarginate or obcordate, surfaces glabrous; venation pinnate. |
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, 0.8–1.1 × 0.7–1 mm, glabrous; glands 4, elliptic to trapezoidal, 0.3–0.6 × 0.6–1.2 mm; horns divergent, 0.5–1 mm. |
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 smooth, glabrous; styles 0.6–1 mm, 2-fid. |
Capsules | globose, 1.8–3 × 2.5–4.8 mm, glabrous or sparsely strigose; columella 2.3–2.5 mm. |
depressed-globose, 1.8–2.2 × 2.2–2.9 mm, slightly lobed; cocci rounded to slightly flattened, smooth, glabrous; columella 1.5–1.8 mm. |
Seeds | light gray, ovoid, 2 × 1.2–1.3 mm, smooth or with few, very shallow depressions; caruncle absent. |
reddish brown to brown, often glaucous, oblong, 1.3–1.4 × 0.8–0.9 mm, abaxial faces with 15–20 shallow pits or almost smooth, adaxial faces with 4–6 large shallow pits or irregular oblong grooves; caruncle conic, hat-shaped, 0.3–0.4 × 0.4–0.6 mm. |
Cyathia | in terminal pleiochasia; peduncle 5–15 mm, filiform, glabrous or very sparsely puberulent to sericeous. |
peduncle 0.2–0.6 mm. |
Cyathial | arrangement: terminal pleiochasial branches 3, each 1–3(–4) times 2-branched; pleiochasial bracts obovate, similar in size to distal leaves; dichasial bracts distinct or basally subconnate, not imbricate, triangular-ovate, base truncate or cordate, margins entire, apex mucronate; axillary cymose branches 1–4. |
|
Euphorbia discoidalis |
Euphorbia tetrapora |
|
Phenology | Flowering and fruiting late spring–fall. | Flowering and fruiting spring. |
Habitat | Sand hills, pine savannas, woodland borders, open fields with sandy soils. | Sandy soils, dry open woods. |
Elevation | 0–150 m. (0–500 ft.) | 0–300 m. (0–1000 ft.) |
Distribution |
AL; FL; GA; LA; MS; TX
|
LA; OK; TX |
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 tetrapora is endemic to a portion of the western Gulf coastal plain. D. S. Correll and M. C. Johnston (1970) included Alabama and Georgia in the distribution of this species as well, probably due to Engelmann’s citation of a Georgia specimen from the herbarium of Samuel Boykin. Whether the Boykin specimen came from Georgia, where Boykin was based, is unclear. Because no records to support its occurrence in the eastern Gulf coastal plain (Alabama or Georgia) have been found, those states are here excluded from the distribution of E. tetrapora. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 245. | FNA vol. 12, p. 311. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Alectoroctonum | Euphorbiaceae > Euphorbia > subg. Esula |
Sibling taxa | ||
Synonyms | Tithymalopsis discoidalis | Tithymalus tetraporus |
Name authority | Chapman: Fl. South. U.S., 401. (1860) | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 191. (1859) |
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