Euphorbia chamaesula |
Euphorbia jejuna |
|
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mountain spurge |
dwarf broomspurge |
|
Habit | Herbs, perennial, with thick rootstock. | Herbs, perennial, with woody or fibrous-fleshy, napiform, branched or tuberous taproot, 3–15 mm thick. |
Stems | erect, branched, 40–90 cm, glabrous. |
ascending to erect, densely emerging from woody crown, 5–15 cm, glabrous. |
Leaves | petiole 0.5–1 mm; blade elliptic to oblong, 8–20(–40) × 3–6 mm, base truncate, rounded, or attenuate, margins entire, apex obtuse or acute, sometimes slightly mucronate, surfaces glabrous; venation inconspicuous, only midvein prominent. |
opposite; stipules connate into lacerate or 2-fid, lanceolate or deltate scale, 0.5–0.9 mm, glabrous; petiole 0.3–0.9 mm, glabrous; blade orbiculate-obovate, ovate, or elliptic, 3–6(–8) × 1.8–5 mm, base moderately asymmetric, rounded to truncate, margins entire, apex blunt to acute, surfaces glabrous; 2–3-veined from base but usually only midvein conspicuous. |
Involucre | turbinate or campanulate, 1.5–2.5 × 1.1–1.9 mm, glabrous; glands 4, crescent-shaped to semicircular, 0.5–0.8 × 1–1.8 mm; horns usually convergent, 0.2–0.8 mm. |
broadly campanulate, 1.2–1.5 × 0.8–1.2 mm, glabrous; glands 4, yellowish to green or purplish, oblong, 0.2–0.4 × 0.5–1 mm; appendages erect or spreading, white, 0.3–0.6 × 0.8–1.2 mm, usually deeply dissected into 4–5 acuminate lobes, rarely undivided, when divided distal margin rarely entire or crenate. |
Staminate flowers | 8–12. |
12–35. |
Pistillate flowers | ovary glabrous; styles 1–1.8 mm, 2-fid. |
ovary glabrous; styles 0.4–0.5 mm, unbranched thickened-clavate. |
Capsules | depressed-ovoid, 4.3–5 × 5–6 mm, 3-lobed; cocci rounded, smooth, glabrous; columella 3.5–4 mm. |
ovoid and broadly triangular, 1.8–2.2(–2.7) × 1.5–2.1 mm, glabrous; columella 1.5–2.2 mm. |
Seeds | gray to dark brown, ovoid-oblong, truncate at both ends, 2.6–3.4 × 2–2.6 mm, shallowly pitted to almost smooth; caruncle conic, 1 × 0.8 mm. |
whitish, oblong, 4-angled in cross section, adaxial faces concave, with long raphe between, 1.5–2(–2.3) × 0.6–0.8 mm, dimpled with faint irregular transverse wrinkles or with up to 10 low, rounded transverse ridges. |
Cyathial | arrangement: terminal pleiochasial branches 3–5(–6), each 3–4 times 2-branched; pleiochasial bracts ovate-lanceolate to slightly subpandurate, similar in size or wider than distal leaves; dichasial bracts distinct, lanceolate to broadly ovate, base usually truncate to rounded or subcordate, sometimes attenuate, margins entire or slightly crenulate, apex usually obtuse to acute, occasionally acuminate; axillary cymose branches 2–8. |
|
Cyathia | peduncle 1–3 mm. |
solitary at distal nodes; peduncle 0.8–1.5 mm. |
2n | = 26. |
|
Euphorbia chamaesula |
Euphorbia jejuna |
|
Phenology | Flowering and fruiting spring–summer. | Flowering and fruiting early spring–summer. |
Habitat | Clearings in ponderosa pine forests, montane roadsides, dry streambeds, creek banks, sandy and gravelly soils. | Thin calcareous soils (caliche) on limestone hills. |
Elevation | 1700–2700 m. (5600–8900 ft.) | 500–900 m. (1600–3000 ft.) |
Distribution |
AZ; NM; Mexico (Chihuahua, Sonora)
|
TX; Mexico (Chihuahua, Coahuila) |
Discussion | Euphorbia chamaesula is easily distinguished from other perennial members of subg. Esula in western North America by its larger capsules and the vegetative shoots (without cyathia) that arise from the distal nodes of the stem proximal to the pleiochasia. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Euphorbia jejuna is known in the flora area from only a few collections in Mitchell, Nolan, Terrell, and Val Verde counties. The species is very similar to E. astyla, but differs in its more deeply divided involucral gland appendages and more definitely petiolate, rounder leaves. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 12, p. 300. | FNA vol. 12, p. 274. |
Parent taxa | Euphorbiaceae > Euphorbia > subg. Esula | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | Tithymalus chamaesula | Chamaesyce jejuna |
Name authority | Boissier: Cent. Euphorb., 38. (1860) | M. C. Johnston & Warnock: SouthW. Naturalist 5: 97, fig. [p. 98]. (1960) |
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