Euphorbia spathulata |
Euphorbia stictospora |
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prairie spurge, reticulate seed spurge, spatulate leaf spurge, warty spurge |
mat spurge, narrow-seed spurge, slimseed sandmat |
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Habit | Herbs, usually annual, rarely biennial, with taproot. | Herbs, annual, with taproot. |
Stems | erect or ascending, unbranched or branched, 10–70 cm, glabrous. |
prostrate, often mat-forming, occasionally with ascending tips, 5–45 cm, densely and evenly pilose to lanate. |
Leaves | petiole absent or to 0.2 mm; blade oblanceolate, oblong-oblanceolate, spatulate, or cuneate, 10–50 × 6–11 mm, base broadly attenuate to rounded or shallowly cordate-clasping, margins finely serrulate (usually distally), apex usually rounded to obtuse, occasionally slightly retuse or obcordate proximally, bluntly mucronate, surfaces glabrous; venation pinnate, midvein prominent. |
opposite; stipules distinct or connate basally on one side of stem, entire or irregularly toothed or fringed, 0.5–1.2 mm, pilose to lanate; petiole 0.3–1.5 mm, pilose to lanate; blade usually oblong to oblong-obovate, occasionally nearly circular, 3–10(–15) × 2–5(–10) mm, base asymmetric, one side usually angled or rounded and other truncate-auriculate, margins minutely or conspicuously serrulate at least toward apex, apex usually broadly rounded to broadly acute, occasionally emarginate, abaxial surface often ± lighter green and without reddish spot, both surfaces sparsely to moderately pilose to lanate; 3-veined from base or venation obscure. |
Involucre | campanulate to cupulate, 0.6–1(–1.5) × 0.8–1.2 mm, glabrous; glands 4–5, elliptic, oblong, to slightly reniform, 0.2–0.6 × 0.4–1 mm; horns absent. |
obconic, 0.7–1 × 0.4–0.6 mm, moderately to densely pilose to lanate; glands 4, reddish, ± unequal, oblong, 0.1 × 0.1–0.3 mm; appendages white to strongly pinkish or reddish tinged, often unequal, sometimes 1 to all absent, 0–0.3 × 0–0.4 mm, 3-lobed or rudimentarily 1-lobed, distal margin crenate. |
Staminate flowers | 3–10. |
3–9. |
Pistillate flowers | ovary glabrous; styles 0.8–1.5 mm, 2-fid. |
ovary pilose to villous, hairs occasionally slightly appressed; styles 0.2–0.5 mm, unbranched or inconspicuously notched at tip. |
Capsules | depressed-globose, 2–3.5 × 4 mm, 3-lobed; cocci rounded, verrucose, verrucae 0.1–0.2 mm, glabrous; columella 1.4–2.2 mm. |
ovoid, 1.6–2.3 × 1.4–1.5 mm, moderately to densely villous with hairs usually slightly appressed, pubescence often concentrated on proximal 1/2 or along lobes; columella 1.5–2 mm. |
Seeds | red-brown to dark purple, occasionally ± glaucous, broadly ellipsoid-ovoid to nearly globose, 1.3–2.5 × 1.5–1.8 mm, smooth, reticulate, or finely low-ridged; caruncle irregularly reniform to round, subconic to lenticular, 0.3–0.4 × 0.5–0.6 mm. |
light to dark brown, usually mottled, sometimes with thin, white coating, often wearing away irregularly, narrowly oblong-ovoid to ellipsoid, 3–4-angled in cross section, 1–1.5 × 0.5–0.6 mm, with short, irregularly interrupted furrows, appearing partially and irregularly few-ridged. |
Cyathial | arrangement: terminal pleiochasial branches 3(–5), each 1–3 times 2-branched; pleiochasial bracts broadly ovate to ovate-oblong, shorter and wider than distal leaves; dichasial bracts distinct, broadly ovate, ovate-triangular, or ovate-elliptic, base cordate-clasping or subcordate to rounded, margins serrulate, apex rounded to obtuse or acute; axillary cymose branches (0–4)5–12. |
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Cyathia | peduncle 0.3–1(–1.5) mm. |
solitary at leaf nodes or in small, cymose clusters on congested, axillary branches; peduncle 0.7–2.5 mm. |
Euphorbia spathulata |
Euphorbia stictospora |
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Phenology | Flowering and fruiting spring–summer. | Flowering and fruiting midsummer–early fall. |
Habitat | Forests, fallow fields, prairies, pastures, glades, stream banks, waste places, roadsides. | Open disturbed areas, rocky slopes. |
Elevation | 0–3500 m. (0–11500 ft.) | 100–2100 m. (300–6900 ft.) |
Distribution |
AL; AR; AZ; CA; CO; DC; FL; GA; IA; ID; IL; IN; KS; KY; LA; MD; MI; MN; MO; MS; MT; NC; ND; NE; NM; OH; OK; OR; PA; SC; SD; TN; TX; UT; VA; WA; WI; WV; WY; ON; Mexico (Chihuahua, Sonora); s South America
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AZ; CO; IA; KS; MO; ND; NE; NM; OK; SD; TX; WY; Mexico (Chihuahua, Durango, San Luis Potosí)
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Discussion | As treated here, Euphorbia spathulata is a wide-ranging and variable species. J. B. S. Norton (1900) recognized a number of segregates (for example, E. arkansana, E. dictyosperma, and E. obtusata) all of which are included here in a broadly defined E. spathulata. The only segregate species that has been widely recognized in regional floras is E. obtusata (for example, M. L. Fernald 1950; T. S. Cooperrider 1995; G. Yatskievych 1999–2013, vol. 2). Authors have generally distinguished the eastern North American E. obtusata from the western E. spathulata by the former's larger seeds (1.7–2.3 mm versus 1.5–1.7 mm) with smooth (versus reticulate) surfaces, larger involucres, red (versus yellow) involucral glands, and cordate-clasping (versus rounded to subcordate) dichasial bracts. Examination of specimens of E. spathulata in the broad sense from throughout North America showed that there is some geographic patterning to seed size and surface sculpturing, but the variation does not segregate cleanly into two discrete taxa. Plants from western North America typically have small seeds (1.5–1.7 mm) with reticulate surfaces, although some western individuals have seeds 1.8–1.9 mm long with reticulate surfaces. Plants from Texas generally have small seeds (1.5–1.6 mm) but with the surfaces either reticulate or completely smooth. Plants from adjacent Louisiana have small seeds with faintly reticulate to almost bumpy surfaces. Plants from eastern North America have larger seeds (2–2.3 mm) with usually smooth surfaces, although individuals from Tennessee and the Carolinas have faintly reticulate surfaces. Involucre height, gland color, and the shape of the dichasial bracts do not segregate with seed size as previous treatments have suggested. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Euphorbia stictospora has been recorded from New York, but this disjunct occurrence likely represents a waif or misidentification. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 309. | FNA vol. 12, p. 289. |
Parent taxa | Euphorbiaceae > Euphorbia > subg. Esula | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | E. arkansana, E. dictyosperma, E. obtusata, Galarhoeus arkansanus, G. obtusatus, Tithymalus arkansanus, T. dictyospermus, T. obtusatus, T. spathulatus | Chamaesyce stictospora |
Name authority | Lamarck: in J. Lamarck et al., Encycl. 2: 428. (1788) | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 187. (1859) |
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