Euphorbia chaetocalyx |
Euphorbia macropus |
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bristlecup sandmat |
Huachuca Mountain spurge |
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Habit | Herbs, perennial, with woody, thickened taproot. | Herbs, perennial, with thick, globose to elongated tubers, 2–8 cm. | ||||
Stems | usually erect, rarely slightly decumbent, often densely clustered from top of woody crown, 3–15 cm, glabrous. |
erect to ascending, branched, 10–45(–60) cm, glabrous, puberulent, or densely hirsute to setose, often with 2-layered indumentum of long hairs intermixed with short hairs. |
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Leaves | opposite; stipules distinct, narrowly linear, usually entire, 0.5–1 mm, glabrous; petiole 0.5–1 mm, glabrous; blade ovate to lanceolate or oblong- or linear-lanceolate, 3–11 × 0.8–3(–5) mm, base slightly asymmetric, short-tapered, occasionally one side slightly rounded, margins entire, apex acute or short-acuminate, surfaces glabrous; only midvein conspicuous. |
usually opposite, occasionally whorled distally, or rarely with 1–2 alternate leaves; stipules 0.1–0.2 mm; petiole 0–18 mm, hirsute, sericeous, or strigose; blade linear to ovate or almost orbiculate, 6–54 × 2–19 mm, base rounded to attenuate, margins entire, occasionally ciliate with stiff recurved hairs, apex acute to obtuse, surfaces usually hirsute, sericeous, or strigose, occasionally glabrous adaxially; venation conspicuous. |
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Involucre | campanulate to turbinate, 0.8–1.4 × 0.8–1 mm, glabrous; glands 4, yellow-brown to reddish, concave or convex, elliptic or oval, 0.2–0.4 × 0.4–0.6 mm; appendages absent or white, lanceolate-deltate to straplike, 0.2–1.1 × 0.2–0.9 mm, distal margin entire, crenate, or deeply cleft or divided. |
obconic to campanulate, 1.1–1.4 × 0.5–1.5 mm, glabrous or strigillose; glands 4–5, greenish, oblong, 0.2 × 0.4–0.5 mm; appendages usually yellowish or green, rarely dark purple, ovate, flabellate, semiorbiculate, or oblong, 0.3–0.9 × 0.4–1.1 mm, usually entire. |
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Staminate flowers | 25–35. |
10–15. |
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Pistillate flowers | ovary glabrous; styles 0.3–0.4 mm, 2-fid 1/2 length. |
ovary glabrous, sericeous, or strigillose; styles 0.4–0.6 mm, 2-fid 1/2 length. |
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Capsules | depressed-ovoid to depressed-globose, 1.7–2.1 × 1.6–2.4 mm, glabrous; columella 1.2–1.8 mm. |
oblate, 2.3–3 × 3.1–4.2 mm, glabrous, sericeous, or strigillose; columella 1.6–2.1 mm. |
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Seeds | white, ovoid-pyramidal, prominently 4-angled in cross section, 1.6–2 × 1–1.2 mm, smooth to slightly wrinkled. |
black to light brown, broadly ovoid to subglobose, rounded in cross section, 1.5–2.3 × 1.4–1.8 mm, smooth or with low rounded tubercles; caruncle absent. |
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Cyathia | solitary at distal nodes; peduncle 0.8–1.3 mm. |
in weakly-defined terminal dichasia; peduncle 1.4–5.8 mm, glabrous. |
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Euphorbia chaetocalyx |
Euphorbia macropus |
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Phenology | Flowering and fruiting summer–fall. | |||||
Habitat | Stream banks and rocky slopes in pine-oak woodlands, sometimes with juniper, Douglas fir-pine forests. | |||||
Elevation | 1500–2200m. (4900–7200ft.) | |||||
Distribution |
AZ; NM; TX; n Mexico
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AZ; Mexico; Central America (Guatemala, Honduras) |
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Discussion | Varieties 2 (2 in the flora). Euphorbia chaetocalyx is similar to E. fendleri but can generally be distinguished from that species by its narrow, acute leaves and ± erect stems. Some authors have used the presence or absence and shape of the involucral gland appendages to help separate E. chaetocalyx from E. fendleri, but those characters appear highly variable and of little taxonomic utility. Some individuals from western Texas (Culberson and El Paso counties) and southern New Mexico appear intermediate with E. fendleri. The specific epithet of E. chaetocalyx refers to the bristly perianthlike segments that subtend the ovary, but these structures are found intermittently in both E. chaetocalyx and E. fendleri. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Euphorbia macropus is a widespread and common Mexican species just barely entering the flora area in southeastern Arizona, where most of the collections are from the Huachuca Mountains. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 12, p. 263. | FNA vol. 12, p. 248. | ||||
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > sect. Alectoroctonum | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | E. fendleri var. chaetocalyx, Chamaesyce chaetocalyx | Anisophyllum macropus, E. biformis, E. plummerae | ||||
Name authority | (Boissier) Tidestrom: Proc. Biol. Soc. Wash. 48: 40. (1935) | (Klotzsch & Garcke) Boissier: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 15(2): 52. (1862) | ||||
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