Euphorbia bicolor |
Euphorbia wrightii |
|
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snow-on-the-prairie |
Wright's spurge |
|
Habit | Herbs, annual, with taproot. | Herbs, perennial with cylindric rootstock or elongated tubers. |
Stems | erect, unbranched or branched, 40–100 cm, pilose. |
erect, branched, densely clumped, previous year’s dead stems often persistent, 20–50 cm, glabrous. |
Leaves | alternate; stipules 0.3–0.4 mm; petiole 0.3–1 mm, pilose; blade narrowly elliptic to lanceolate, 37–54 × 7–17 mm, base cuneate to slightly rounded, margins entire, apex aristate or acute, surfaces pilose; venation obscure, only midvein conspicuous. |
alternate, persisting, spreading or ascending; stipules 0.1–0.3 mm; petiole absent; blade linear to linear-filiform, (17–)20–40 × 1–2.5 mm, base cuneate, slightly sheathing stem, margins entire, apex broadly acute to rounded, abaxial surface glabrous or sparsely villous, adaxial surface glabrous; venation obscure, only midvein conspicuous on wider leaves. |
Involucre | campanulate, 2.7–3.5 × 2.2–3 mm, densely pilose; glands 4–5, green to pale greenish yellow, reniform, 0.6–0.7 × 1.4–1.6 mm; appendages white, obdeltate to orbiculate, 1.4–2.5 × 1.7–3 mm, dentate to erose. |
campanulate, 1.5–2 × 1.8–2.5 mm, pilose; glands 5, green, broadly elliptic, 0.7–0.8 × 1 mm; appendages white to pink, orbiculate, 0.5–1 × 1.3–1.8 mm, coarsely erose. |
Staminate flowers | 30–70. |
20–25. |
Pistillate flowers | ovary pilose; styles 0.7–1.2 mm, 2-fid 1/2 length. |
ovary strigose to tomentose; styles 1 mm, 2-fid at apex. |
Capsules | depressed-ovoid, 3.5–7.5 × 6–8.7 mm, densely pilose; columella 4.5–5.5 mm. |
depressed-globose, 1 locule usually aborting, 2.5(–3) × 2.7–3.3(–5) mm, sparsely tomentose; columella 2.6–3 mm. |
Seeds | tan to brown, ovoid, 4.3–4.5 × 3.7–3.9 mm, alveolate; caruncle absent. |
gray-green to gray-brown, globose-ovoid, 2.2–2.9 × 1.8–2 mm, shallowly and obscurely pitted; caruncle absent. |
Cyathia | in terminal pleiochasia dichasial and pleiochasial bracts linear to narrowly oblanceolate, with conspicuous white margins; peduncle 1.2–3 mm, densely pilose. |
usually in terminal dichasia, rarely pleiochasia; peduncle (3–)5–15 mm, all peduncles and cyathia persistent on plant, glabrous. |
Euphorbia bicolor |
Euphorbia wrightii |
|
Phenology | Flowering and fruiting summer–fall. | Flowering and fruiting spring–fall. |
Habitat | Prairies, blackland (calcareous) prairies, pastures and clearings in former blackland prairie areas, roadside clearings. | Open grasslands and uplands, often on limestone outcrops. |
Elevation | 100–200 m. (300–700 ft.) | 500–1000 m. (1600–3300 ft.) |
Distribution |
AR; LA; OK; TX
|
TX; Mexico (Coahuila) |
Discussion | Euphorbia bicolor is similar in appearance to E. marginata but can be distinguished by its linear to narrowly oblanceolate bracts and the presence of hairs on all parts of the plant. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Within the flora area, Euphorbia wrightii is endemic to the western Edwards Plateau and adjacent rolling plains in western Texas. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 243. | FNA vol. 12, p. 251. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Alectoroctonum | Euphorbiaceae > Euphorbia > sect. Alectoroctonum |
Sibling taxa | ||
Name authority | Engelmann & A. Gray: Boston J. Nat. Hist. 5: 233. (1845) | Torrey & A. Gray: in War Department [U.S.], Pacif. Railr. Rep. 2(4): 174. (1857) |
Web links |