Euphorbia geyeri |
Euphorbia exigua |
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Geyer's sandmat, Geyer's spurge |
dwarf spurge, small spurge |
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Habit | Herbs, annual, with taproot. | Herbs, annual, with taproot. | ||||
Stems | prostrate or slightly ascending, loosely mat-forming, 4–25(–45) cm, glabrous. |
erect, unbranched or branched, 3–30 cm, glabrous. |
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Leaves | opposite; stipules usually distinct, occasionally connate basally on lower side, usually deeply parted into 3 or more filiform segments, 0.7–1.5 mm, glabrous; petiole 1–2 mm, glabrous; blade oblong to oblong-obovate or oblong-elliptic, 4–12 × 2–6 mm, base slightly asymmetric, angled or rounded, with one side usually expanded into small, rounded auricle, margins entire, apex usually truncate, occasionally emarginate, abaxial surface pale grayish green, both surfaces glabrous; only midvein conspicuous or venation obscurely pinnate (larger leaves). |
petiole 0–0.5 mm; blade linear, linear-oblong, or linear-spatulate, 2–30 × 1–5 mm, base cuneate or truncate, margins entire, apex acute, obtuse, or emarginate, surfaces glabrous; venation inconspicuous, only midvein prominent. |
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Involucre | broadly campanulate, 1–1.5 × 0.7–0.9 mm, glabrous; glands 4, green to reddish, elliptic-oblong to nearly circular, slightly cupped to folded, 0.2–0.4 × 0.2–0.6 mm; appendages rudimentary to absent or white to reddish-tinged, usually rounded, sometimes pointed, (0–)0.5–1 × (0–)0.1–1.2 mm, distal margin entire or slightly toothed. |
cupulate, 0.3–0.5 × 0.6–0.8 mm, glabrous; glands 4, elliptic to crescent-shaped, 0.2–0.4 × 0.3–0.6 mm; horns divergent, 0.2–0.5 mm. |
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Staminate flowers | 5–20. |
5–8. |
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Pistillate flowers | ovary glabrous; styles 0.2–0.6 mm, 2-fid nearly 1/2 length. |
ovary glabrous; styles 0.5–0.7 mm, 2-fid. |
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Capsules | globose-ovoid, 1.5–2 × 1.5–3 mm, glabrous; columella 1.5–1.9 mm. |
subglobose, 1–1.8 × 1.3–2 mm, slightly lobed; cocci rounded, smooth, puncticulate toward abaxial line, glabrous; columella 1.1–1.4 mm. |
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Seeds | ashy white, ovoid, terete to bluntly subangled in cross section, 1.1–1.7 × 0.9–1.2 mm, smooth, with smooth brown line from top to bottom on adaxial side. |
blackish to grayish, 4-angled-ovoid, 1–1.5 × 0.5–0.7 mm, white, tuberculate; caruncle conic or subconic, 0.1–0.3 × 0.1–0.3 mm. |
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Cyathia | solitary or in small, cymose clusters at distal nodes; peduncle 1–2 mm. |
peduncle 0–2 mm. |
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Cyathial | arrangement: terminal pleiochasial branches 3–5, each 1–3 times 2-branched; pleiochasial bracts similar in shape and size to or sometimes slightly longer and wider than distal leaves; dichasial bracts distinct, linear, or linear-lanceolate, or lanceolate-ovate, base rounded to subcordate, margins entire, apex acute; axillary cymose branches 0–5. |
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Euphorbia geyeri |
Euphorbia exigua |
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Phenology | Flowering and fruiting summer–fall. | |||||
Habitat | Edges of gardens, roadsides, waste places. | |||||
Elevation | 0–1500 m. (0–4900 ft.) | |||||
Distribution |
CO; IA; IL; IN; KS; LA; MI; MN; MO; MS; MT; ND; NE; NM; OK; SD; TX; UT; WI; WY; MB; n Mexico
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CA; NY; WV; BC; NS; ON; Europe; w Asia; n Africa; Atlantic Islands (Macaronesia) [Introduced in North America] |
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Discussion | Varieties 2 (2 in the flora). The two varieties of Euphorbia geyeri have been distinguished in large part by the presence of conspicuous involucral gland appendages in var. geyeri and the lack of appendages in var. wheeleriana. The two varieties are recognized here, but the variation in the size and presence of involucral gland appendages in the closely related E. bombensis suggests that this might be a somewhat variable character in this group of species. Euphorbia geyeri is widespread throughout the central United States in sandy soils. Populations at the eastern edge of the range are often considered adventive (for example, sandy soils along railroad grades in Michigan). Euphorbia geyeri resembles E. glyptosperma (both being entirely glabrous), but that species has serrulate leaves (near the apex) and strongly angled, transverse-ridged seeds whereas E. geyeri has entire leaves and smooth, rounded seeds. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Euphorbia exigua can be easily distinguished from other annual species of the genus in the flora area by its tuberculate seeds. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 12, p. 268. | FNA vol. 12, p. 302. | ||||
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > subg. Esula | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Chamaesyce geyeri | Tithymalus exiguus | ||||
Name authority | Engelmann: Boston J. Nat. Hist. 5: 260. (1845) | Linnaeus: Sp. Pl. 1: 456. (1753) | ||||
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