Euphorbia commutata |
Euphorbia humistrata |
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tinted euphorbia, tinted woodland spurge |
spreading sandmat |
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Habit | Herbs, usually biennial, occasionally annual, with taproot. | Herbs, annual, with taproot. |
Stems | erect or ascending, decumbent and often branched near base, 10–40 cm, glabrous. |
prostrate to ascending, usually mat-forming and rooting at nodes, 5–45 cm, sparsely to moderately villous to pilose (densely on young growth). |
Leaves | petiole usually 5–10 mm, 0–1 mm distally; blade usually oblanceolate to obovate, rarely ovate, 5–30 × 3–10 mm, base broadly attenuate, margins entire, apex usually obtuse to rounded, occasionally slightly retuse, surfaces glabrous; venation pinnate, midvein prominent. |
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. |
Involucre | campanulate, 1.7–2.5 × 1.5–2.5 mm, glabrous; glands 4, crescent-shaped; 0.6–1 × 0.8–1.5 mm; horns divergent, 0.5–1.1 mm. |
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. |
Staminate flowers | 9–15. |
2–5. |
Pistillate flowers | ovary glabrous; styles 0.9–1.3 mm, 2-fid. |
ovary short-sericeous; styles 0.5–0.8 mm, 2-fid 1/2 length. |
Capsules | ovoid-globose, 2.5–3.2 × 3 mm, slightly lobed; cocci rounded to ± flattened, smooth, glabrous; columella 1.5–2 mm. |
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. |
Seeds | white to gray, broadly oblong-elliptic to ovoid or nearly globose, 1.5–2 × 1.3–1.6 mm, strongly small-pitted; caruncle irregularly winglike, conic, 0.6–1 × 0.7–0.9 mm. |
white to light brown, oblong-ovoid, bluntly angular in cross section, 0.8–1.2 × 0.5–0.9 mm, smooth or papillate. |
Cyathial | arrangement: terminal pleiochasial branches (2–)3(–4), 1–3+ times 2-branched; pleiochasial bracts similar in shape and size to distal leaves; dichasial bracts distinct to basally subconnate, not imbricate, widely ovate, rhombic, or reniform, base cordate, rarely slightly perfoliate, margins entire, apex obtuse to rounded, mucronulate; axillary cymose branches 0–5. |
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Cyathia | peduncle 0.5–1 mm. |
solitary at distal nodes; peduncle 0.1–0.6(–2) mm. |
Euphorbia commutata |
Euphorbia humistrata |
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Phenology | Flowering and fruiting spring–summer. | Flowering and fruiting spring–late summer. |
Habitat | Bottomland and upland forests, bluffs and ledges, stream banks, glades, rarely fen margins. | Stream and river banks, gravel bars, floodplains, pond edges, disturbed fields, railroads, roadsides. |
Elevation | 50–1000 m. (200–3300 ft.) | 0–300 m. (0–1000 ft.) |
Distribution |
AL; AR; FL; GA; IA; IL; IN; KY; LA; MD; MI; MO; MS; NC; OH; OK; PA; SC; TN; VA; WI; WV; ON
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AL; AR; FL; GA; IL; IN; KS; KY; LA; MO; MS; OH; OK; TN; TX; VA; WV
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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.) |
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Source | FNA vol. 12, p. 300. | FNA vol. 12, p. 272. |
Parent taxa | Euphorbiaceae > Euphorbia > subg. Esula | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | Galarhoeus austrinus, G. commutatus, Tithymalus commutatus | Chamaesyce humistrata |
Name authority | Engelmann: in A. Gray, Manual ed. 2, 389. (1856) | Engelmann: in A. Gray, Manual ed. 2, 386. (1856) |
Web links |