Euphorbia geyeri |
Euphorbia stictospora |
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Geyer's sandmat, Geyer's spurge |
mat spurge, narrow-seed spurge, slimseed sandmat |
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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. |
prostrate, often mat-forming, occasionally with ascending tips, 5–45 cm, densely and evenly pilose to lanate. |
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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). |
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. |
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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. |
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. |
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Staminate flowers | 5–20. |
3–9. |
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Pistillate flowers | ovary glabrous; styles 0.2–0.6 mm, 2-fid nearly 1/2 length. |
ovary pilose to villous, hairs occasionally slightly appressed; styles 0.2–0.5 mm, unbranched or inconspicuously notched at tip. |
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Capsules | globose-ovoid, 1.5–2 × 1.5–3 mm, glabrous; columella 1.5–1.9 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. |
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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. |
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. |
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Cyathia | solitary or in small, cymose clusters at distal nodes; peduncle 1–2 mm. |
solitary at leaf nodes or in small, cymose clusters on congested, axillary branches; peduncle 0.7–2.5 mm. |
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Euphorbia geyeri |
Euphorbia stictospora |
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Phenology | Flowering and fruiting midsummer–early fall. | |||||
Habitat | Open disturbed areas, rocky slopes. | |||||
Elevation | 100–2100 m. (300–6900 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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AZ; CO; IA; KS; MO; ND; NE; NM; OK; SD; TX; WY; Mexico (Chihuahua, Durango, San Luis Potosí)
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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 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.) |
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Key |
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Source | FNA vol. 12, p. 268. | FNA vol. 12, p. 289. | ||||
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > sect. Anisophyllum | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Chamaesyce geyeri | Chamaesyce stictospora | ||||
Name authority | Engelmann: Boston J. Nat. Hist. 5: 260. (1845) | Engelmann: in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 187. (1859) | ||||
Web links |