Euphorbia lurida |
Euphorbia schizoloba |
|
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woodland spurge |
Mojave spurge |
|
Habit | Herbs, perennial, with thick rootstock. | Herbs, perennial, with thick rootstock. |
Stems | erect or ascending, unbranched, sometimes sinuous, 5–30 cm, glabrous or sparsely to densely puberulent. |
slender, ascending, often sinuous, many, densely branched near base, 10–50 cm, usually glabrous, usually glaucous. |
Leaves | petiole 0–1 mm; blade oblanceolate to obovate, 8–20 mm × 3–7 mm, base truncate or cuneate, margins entire, apex obtuse to rounded, minutely mucronate, surfaces puberulent or glabrous; venation inconspicuous, only midvein prominent. |
petiole 0–1 mm; blade broadly oblanceolate to obovate, 10–20 × 3–9 mm, base usually acute, occasionally short-attenuate, rarely obtuse, margins entire, apex usually acute, occasionally obtuse, acuminate to cuspidate, surfaces usually glabrous, usually glaucous; venation pinnate, sometimes obscure, midvein prominent. |
Involucre | cupulate, 2–2.2 × 1.3–1.8 mm, glabrous; glands 4, oblong to broadly ovate, usually truncate, 0.5–0.8 × 1–1.6 mm, margins irregularly crenate to strongly dentate; horns absent or usually divergent or straight, 0.1–0.3 mm, usually slightly longer than, occasionally equaling, teeth on gland margin. |
campanulate to broadly turbinate, 2.2–3 × 2–2.5 mm, glabrous; glands 4, irregularly semicircular to trapezoidal or elliptic-truncate, 0.8–1.5 × 1–2.2, margins strongly crenate or dentate; horns usually absent, if present then straight, 0.1–0.2 mm, generally equaling teeth on gland margin. |
Staminate flowers | 10–20. |
12–20. |
Pistillate flowers | ovary glabrous or puberulent; styles 0.7–1 mm, 2-fid. |
ovary glabrous; styles 1–1.2 mm, 2-fid. |
Capsules | ovoid, 3.5–4 × 4–4.5 mm, 3-lobed; cocci rounded, smooth to slightly rugose, glabrous; columella 3.2–3.5 mm. |
oblong-ovoid, 3.5–4 × 3.8–5 mm, 3-lobed; cocci rounded, smooth, glabrous; columella 3.3–3.8 mm. |
Seeds | gray to dark gray, truncate-oblong to truncate-ovoid, 2.8–3 × 1.7–2 mm, irregularly pitted; caruncle conic, 0.6 × 0.7 mm. |
gray to whitish, oblong cylindric, 2–3 × 1.5 mm, irregularly shallowly pitted to almost smooth; caruncle conic, 0.6 × 0.6 mm. |
Cyathial | arrangement: terminal pleiochasial branches 3–5, each 1–4 times 2-branched; pleiochasial bracts ovate to broadly ovate or oblanceolate, wider than distal leaves; dichasial bracts distinct, rounded, oblanceolate, or subreniform, base cuneate or obtuse, margins entire, apex obtuse, slightly mucronate; axillary cymose branches 0–4. |
arrangement: terminal pleiochasial branches (1–)3–4(–5), each 1–3 times 2-branched; pleiochasial bracts broadly ovate to subcordate, usually similar in size to, occasionally wider than, distal leaves; dichasial bracts distinct, broadly ovate to almost reniform, base obtuse, margins entire, apex obtuse, acuminate to cuspidate; axillary cymose branches 0–2(–4). |
Cyathia | peduncle 0.3–0.9 mm. |
peduncle 0.3–1 mm. |
Euphorbia lurida |
Euphorbia schizoloba |
|
Phenology | Flowering and fruiting spring–summer. | Flowering and fruiting spring–summer. |
Habitat | Open pine-oak forests, dry slopes and canyons. | Desert mountains and canyon slopes, rocky and gravelly soils. |
Elevation | 1300–2800 m. (4300–9200 ft.) | 500–1800 m. (1600–5900 ft.) |
Distribution |
AZ; CA; NM; NV; UT; Mexico (Baja California)
|
AZ; CA; NV
|
Discussion | Euphorbia lurida has been treated as a complex of several taxa in the past, but only a single, broadly-defined species is recognized here. This species is variable in both the pubescence and shape of the bracts subtending the cyathia and also in the degree of crenation of the gland margin. In the northern part of its range, E. lurida appears to intergrade with E. brachycera, and it can be difficult to distinguish these two species in northern Arizona and New Mexico. A report of the species from Sonora, Mexico, based on a single immature collection (V. W. Steinmann and R. S. Felger 1997) has not been verified. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Euphorbia schizoloba is a desert perennial that occurs on bluffs and ledges in the Mojave and Sonoran Deserts. Sparsely pubescent plants of E. schizoloba are known from Arizona and are best represented by several collections from the Mazatzal and Sierra Ancha mountains in Gila County from between 1000 to 1800 meters. George Engelmann published two names for this species almost simultaneously in 1861 (E. schizoloba and E. incisa). Although the authors have not been able to determine which publication has priority, Engelmann himself cited E. incisa as a synonym of E. schizoloba (in W. H. Brewer et al. 1876–1880, vol. 2), as did J. B. S. Norton (1899). Also, the type specimen at MO was annotated by Engelmann as E. schizoloba, and there is no mention of the name E. incisa on the sheet. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 305. | FNA vol. 12, p. 309. |
Parent taxa | Euphorbiaceae > Euphorbia > subg. Esula | Euphorbiaceae > Euphorbia > subg. Esula |
Sibling taxa | ||
Synonyms | E. palmeri, E. palmeri var. subpubens, E. subpubens, Tithymalus luridus, T. palmeri, T. subpubens | E. incisa, Tithymalus incisus, T. schizolobus |
Name authority | Engelmann: in J. C. Ives, Rep. Colorado R. 4: 26. (1861) | Engelmann: Proc. Amer. Acad. Arts 5: 173. (1861) |
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