Euphorbia perennans |
Euphorbia humistrata |
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perennial sandmat, Terlingua spurge |
spreading sandmat |
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Habit | Herbs, perennial, with strongly thickened, woody rootstock. | Herbs, annual, with taproot. |
Stems | erect, 7–45 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 | opposite; stipules distinct, linear-filiform in (1–)2(–3) segments, 0.3–0.4 mm, glabrous; petiole 0.8–2 mm, glabrous; blade ovate or orbiculate-deltate to reniform-deltate, 5–17 × 4–16 mm midstem leaves largest, base symmetric, cuneate, rounded to cordate, margins entire, apex acute to rounded, surfaces glabrous, often glaucous; 3-veined from base, only midvein conspicuous. |
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 | broadly-campanulate to hemispheric, 1.7–2.2 × 1.5–2.7 mm, glabrous; glands 4, green to yellow-green, elliptic to oblong, folded longitudinally, 0.3–0.5 × 0.7–1.4 mm; appendages absent. |
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 | 35–45. |
2–5. |
Pistillate flowers | ovary glabrous; styles 0.7–0.9 mm, 2-fid nearly entire length. |
ovary short-sericeous; styles 0.5–0.8 mm, 2-fid 1/2 length. |
Capsules | subglobose to broadly ovoid, 2.8–3.3 × 2.8–3.4 mm, glabrous; columella 2.2–2.7 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 light brown, ovoid, 3–4-angled in cross section, 2–2.4 × 1–1.2 mm, smooth to faintly transverse-wrinkled. |
white to light brown, oblong-ovoid, bluntly angular in cross section, 0.8–1.2 × 0.5–0.9 mm, smooth or papillate. |
Cyathia | solitary at distal nodes or at nodes of short, axillary branches; peduncle 1.8–3 mm. |
solitary at distal nodes; peduncle 0.1–0.6(–2) mm. |
Euphorbia perennans |
Euphorbia humistrata |
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Phenology | Flowering and fruiting spring–fall. | Flowering and fruiting spring–late summer. |
Habitat | Desert scrub, on cretaceous and gypseous clay, limestone hills and flats. | Stream and river banks, gravel bars, floodplains, pond edges, disturbed fields, railroads, roadsides. |
Elevation | 900–1200 m. (3000–3900 ft.) | 0–300 m. (0–1000 ft.) |
Distribution |
TX; Mexico (Chihuahua) |
AL; AR; FL; GA; IL; IN; KS; KY; LA; MO; MS; OH; OK; TN; TX; VA; WV
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Discussion | Euphorbia perennans is a distinctive species with an erect habit and relatively large, firm, deltate midstem leaves. Phylogenetic data place E. perennans in a clade of primarily Chihuahuan Desert annual and perennial species (for example, E. chaetocalyx, E. fendleri, E. golondrina, E. simulans, E. spurca, and E. theriaca; Y. Yang and P. E. Berry 2011). Euphorbia perennans is known in the flora area only from Brewster County. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 12, p. 282. | FNA vol. 12, p. 272. |
Parent taxa | ||
Sibling taxa | ||
Synonyms | Chamaesyce perennans | Chamaesyce humistrata |
Name authority | (Shinners) Warnock & M. C. Johnston: SouthW. Naturalist 5: 170. (1960) | Engelmann: in A. Gray, Manual ed. 2, 386. (1856) |
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