Euphorbia humistrata |
Euphorbia inundata |
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spreading sandmat |
Florida pineland spurge |
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Habit | Herbs, annual, with taproot. | Herbs, perennial, with thickened rootstock. | ||||
Stems | prostrate to ascending, usually mat-forming and rooting at nodes, 5–45 cm, sparsely to moderately villous to pilose (densely on young growth). |
erect or ascending, 15–40 cm. |
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Leaves | opposite; stipules distinct, linear-subulate, often irregularly 2- or 3-lobed, 1–1.3 mm, sparsely villous to pilose; petiole 0.5–1.5 mm, sparsely to moderately villous to pilose; blade oblong-ovate to ovate-elliptic or oblong-elliptic, 4–18 × 2.5–8 mm, base strongly asymmetric, one side angled and other rounded to auriculate, margin on longer side serrulate, on shorter side subentire, apex rounded or broadly acute, abaxial surface pale grayish green, sparsely lanulose, adaxial surface usually with irregular reddish streak along midvein, usually glabrate, rarely sparsely lanulose; palmately veined at base, pinnate distally. |
petiole absent or indistinct, blade linear to linear-elliptic or lanceolate, (25–)30–60(–115) × 1.5–14(–15) mm, chartaceous, base attenuate, apex acuminate, acute, or rounded and mucronate; only midvein evident. |
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Involucre | obconic, 0.8–1 × 0.6–0.8 mm, sparsely villous to pilose; glands 4, green to yellow-green (turning pink with age), usually ± unequal, narrowly oblong, 0.1–0.2 × 0.2–0.5 mm; appendages white to reddish tinged, lunate, ± irregular and variable in shape, 0.1–0.3 × 0.2–1.5 mm, distal margin crenulate. |
obconic or campanulate, 1.3–3.2 × 1.6–3.6 mm, lobes ovate, oblong, or nearly rectangular, 0.6–1 mm, laciniate-ciliate; glands red to greenish, oblong or nearly circular, 0.8–1 × 1.1–2 mm, distal margins crenulate-erose, undulate, or entire. |
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Staminate flowers | 2–5. |
20–25. |
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Pistillate flowers | ovary short-sericeous; styles 0.5–0.8 mm, 2-fid 1/2 length. |
gynophore exserted 2.6–6.1 mm, calyxlike lobes triangular to subulate, 0.6–1.4 mm; styles connate 1/8 length, 1.3–2.2 mm. |
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Capsules | ovoid, well exserted from involucre at maturity, 1.3–1.5 × 1.2–1.6 mm, sparsely to moderately short-sericeous; columella 0.9–1.2 mm. |
oblate-ovoid, 5.1–6.1 × 6.9–8.6 mm, 3-lobed; columella 3.9–4.7 mm. |
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Seeds | white to light brown, oblong-ovoid, bluntly angular in cross section, 0.8–1.2 × 0.5–0.9 mm, smooth or papillate. |
brown to blackish, ovoid-globose, circular or faintly 3- or 4-angled in cross section, 2.9–3.4 × 2.7–3 mm, smooth, base flattened or rounded, apex rounded or with inconspicuous blunt point. |
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Cyathia | solitary at distal nodes; peduncle 0.1–0.6(–2) mm. |
peduncle 6–24 mm (often exceeding dichasial bracts). |
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Cyathial | arrangement: terminal pleiochasial branches 2–3, 5–18 cm, 3–8 times 2-branched; pleiochasial bracts linear-lanceolate or narrowly ovate, 25–49 × 5–9 mm, margins entire, apex acute or acuminate; dichasial bracts ovate or lanceolate, 6–21 × 2–6 mm, margins entire, apex acute or acuminate; axillary cymose branches 1–5. |
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Euphorbia humistrata |
Euphorbia inundata |
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Phenology | Flowering and fruiting spring–late summer. | |||||
Habitat | Stream and river banks, gravel bars, floodplains, pond edges, disturbed fields, railroads, roadsides. | |||||
Elevation | 0–300 m. (0–1000 ft.) | |||||
Distribution |
AL; AR; FL; GA; IL; IN; KS; KY; LA; MO; MS; OH; OK; TN; TX; VA; WV
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AL; FL; GA; MS |
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Discussion | Euphorbia humistrata is distributed throughout the Mississippi River valley and along other major river systems in the central and eastern United States. There are scattered reports of this species as a waif or as introduced farther north and/or east (for example, Minnesota, New York, North Carolina, Ontario, South Dakota, and Wisconsin), but the authors have not been able to verify these occurrences. Euphorbia humistrata is similar to E. maculata and is often confused with that species in herbaria. It can be distinguished from E. maculata by its tendency to root at the stem nodes, its longer styles, and its seeds that lack low transverse ridges and that are more bluntly angled. When growing side-by-side, E. humistrata has an overall less congested appearance and its cyathia are not as numerous or crowded as those of E. maculata. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Varieties 2 (2 in the flora). Euphorbia inundata has a disjunct distribution in the southeastern United States. Allopatric, narrow-leaved populations from the west-central Florida peninsula are segregated as var. garrettii (E. L. Bridges and S. L. Orzell 2002). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 12, p. 272. | FNA vol. 12, p. 314. | ||||
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > sect. Nummulariopsis | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | Chamaesyce humistrata | Galarhoeus inundatus | ||||
Name authority | Engelmann: in A. Gray, Manual ed. 2, 386. (1856) | Torrey ex Chapman: Fl. South. U.S., 402. (1860) | ||||
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