Euphorbia chaetocalyx |
Euphorbia golondrina |
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bristlecup sandmat |
Boquillas sandmat, canyon spurge, swallow spurge |
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Habit | Herbs, perennial, with woody, thickened taproot. | Herbs, annual, with slender taproot. | ||||
Stems | usually erect, rarely slightly decumbent, often densely clustered from top of woody crown, 3–15 cm, glabrous. |
prostrate, 5–35 cm, glabrous. |
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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. |
opposite; stipules distinct, subulate, 0.5–0.8 mm, glabrous; petiole 0.8–1 mm, glabrous; blade oblong, ovate-oblong, to narrowly elliptic-oblong, 5–11.5 × 1–4 mm, base asymmetric, cuneate to rounded, margins entire, thickened and often revolute on drying, apex obtuse, surfaces glabrous; only midvein 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. |
turbinate, 0.9–1.5 × 0.8–1.3 mm, glabrous; glands 4, occasionally rudimentary, red to purple, deeply concave, subcircular, 0.3–0.4 × 0.3–0.4 mm; appendages white, semilunate to slightly flabellate, 0.1–0.3 × 0.5–0.8 mm, distal margin entire. |
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Staminate flowers | 25–35. |
28–40. |
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Pistillate flowers | ovary glabrous; styles 0.3–0.4 mm, 2-fid 1/2 length. |
ovary glabrous; styles 0.3–0.4 mm, 2-fid nearly entire 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. |
broadly ovoid, 1.7–2 × 1.5–1.6 mm, glabrous; columella 1.4–1.7 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. |
narrowly pyramidal-ovoid, 4-angled in cross section, 1.3–1.5 × 0.6–0.7 mm, with very faint transverse ridges or wrinkles. |
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Cyathia | solitary at distal nodes; peduncle 0.8–1.3 mm. |
solitary at distal nodes; peduncle 0.9–1.5 mm. |
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Euphorbia chaetocalyx |
Euphorbia golondrina |
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Phenology | Flowering and fruiting late spring–fall. | |||||
Habitat | Deep, sandy riverbanks. | |||||
Elevation | 600 m. (2000 ft.) | |||||
Distribution |
AZ; NM; TX; n Mexico
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TX; Mexico (Chihuahua, Coahuila) |
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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 golondrina was first collected on a sandy riverbank at the entrance of Boquillas Canyon on the Texas/Mexico border, and the species appears to be restricted to the vicinity of the Rio Grande in western Texas and northern Mexico. Aside from the type locality at Boquillas Canyon, E. golondrina has been documented from additional locations along the Rio Grande in Brewster, Hudspeth, and Presidio counties in Texas and from northern Coahuila and Chihuahua, Mexico. Phylogenetic data place E. golondrina in a clade of primarily Chihuahuan desert annual and perennial herbaceous species (for example, E. chaetocalyx, E. fendleri, E. perennans, E. simulans, E. spurca, and E theriaca; Y. Yang and P. E. Berry 2011). Euphorbia golondrina is superficially similar to other glabrous species in western Texas (for example, E. micromera and E. theriaca), but E. micromera and E. theriaca either lack involucral gland appendages or have shorter, triangular appendages compared to the typical semilunate appendages in E. golondrina. (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. 269. | ||||
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > sect. Anisophyllum | ||||
Sibling taxa | ||||||
Subordinate taxa | ||||||
Synonyms | E. fendleri var. chaetocalyx, Chamaesyce chaetocalyx | Chamaesyce golondrina | ||||
Name authority | (Boissier) Tidestrom: Proc. Biol. Soc. Wash. 48: 40. (1935) | L. C. Wheeler: Proc. Biol. Soc. Wash. 53: 8. (1940) | ||||
Web links |