Euphorbia abramsiana |
Euphorbia geyeri |
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Abrams' sandmat, Abrams' spurge |
Geyer's sandmat, Geyer's spurge |
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Habit | Herbs, annual, with slender taproot. | Herbs, annual, with taproot. | ||||
Stems | prostrate, mat-forming, 10–35(–50) cm, shortly pilose or puberulent at least proximally, often glabrous distally. |
prostrate or slightly ascending, loosely mat-forming, 4–25(–45) cm, glabrous. |
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Leaves | opposite; stipules distinct, divided into 5–7 subulate-filiform segments, 0.6–1.1 mm, usually glabrous, rarely pilose; petiole 0.5–1 mm, glabrous; blade ovate, elliptic-oblong, or slightly ovate-cordate, 3–11 × 2–5 mm, base asymmetric, truncate to hemicordate, margins serrulate at least toward apex, often entire toward base, apex acute to obtuse, surfaces sometimes with red spot in center, glabrous; usually only the midvein conspicuous. |
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). |
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Involucre | obconic, 0.5–0.6 × 0.4–0.5 mm, glabrous; glands 4, yellowish to pink, circular to oblong, 0.1 × 0.1–0.2 mm; appendages absent, or white to pink, semicircular to broadly ovate, to 0.1 × 0.2 mm, distal margin entire or shallowly lobed. |
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. |
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Staminate flowers | 3–5. |
5–20. |
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Pistillate flowers | ovary glabrous; styles 0.1–0.3 mm, 2-fid nearly entire length. |
ovary glabrous; styles 0.2–0.6 mm, 2-fid nearly 1/2 length. |
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Capsules | ellipsoid to ovoid, 1.3–1.5 × 1.1–1.5 mm, glabrous; columella 1–1.3 mm. |
globose-ovoid, 1.5–2 × 1.5–3 mm, glabrous; columella 1.5–1.9 mm. |
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Seeds | light gray to light brown, narrowly ovoid to ovoid, 4-angled in cross section, 1–1.2 × 0.6–0.7 mm, with 3–5 prominent transverse ridges that often interrupt abaxial keel. |
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. |
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Cyathia | solitary at distal nodes of primary stems or at nodes of short congested axillary branchlets; peduncle 0.2–0.5 mm. |
solitary or in small, cymose clusters at distal nodes; peduncle 1–2 mm. |
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Euphorbia abramsiana |
Euphorbia geyeri |
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Phenology | Flowering and fruiting summer–fall. | |||||
Habitat | Desert scrub and desert grasslands. | |||||
Elevation | -40–1400 m. (-100–4600 ft.) | |||||
Distribution |
AZ; CA; NM; TX; Mexico (Baja California, Baja California Sur, Sonora)
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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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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.) |
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Key |
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Source | FNA vol. 12, p. 259. | FNA vol. 12, p. 268. | ||||
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > sect. Anisophyllum | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Chamaesyce abramsiana | Chamaesyce geyeri | ||||
Name authority | L. C. Wheeler: Bull. S. Calif. Acad. Sci. 33: 109. (1934) | Engelmann: Boston J. Nat. Hist. 5: 260. (1845) | ||||
Web links |