Euphorbia cordifolia |
Euphorbia golondrina |
|
---|---|---|
heartleaf sandmat |
Boquillas sandmat, canyon spurge, swallow spurge |
|
Habit | Herbs, annual, with taproot. | Herbs, annual, with slender taproot. |
Stems | prostrate, occasionally mat-forming, 10–43 cm, glabrous. |
prostrate, 5–35 cm, glabrous. |
Leaves | opposite; stipules usually distinct, occasionally connate at base, filiform, 1–1.2(–2.8) mm, usually glabrous, rarely pilose; petiole 0.4–1 mm, usually glabrous; blade ovate to oblong, 4.4–12 × 2.6–7.6 mm, base asymmetric, cordate to rounded, margins entire, apex rounded to mucronulate, 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. |
Involucre | campanulate, 1–1.3 × 1–1.3 mm, glabrous; glands 4, yellowish to pink, elliptic, 0.3–0.5 × 0.5–1 mm; appendages whitish to pink, sometimes drying red, elliptic to ovoid, 1.1–1.5 × 1.2–1.9 mm, distal margin entire, retuse, or erose. |
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. |
Staminate flowers | 5–40. |
28–40. |
Pistillate flowers | ovary glabrous; styles 0.5–0.8 mm, 2-fid nearly entire length. |
ovary glabrous; styles 0.3–0.4 mm, 2-fid nearly entire length. |
Capsules | ovoid, 2–3 mm diam., glabrous; columella 1.2–2.7 mm. |
broadly ovoid, 1.7–2 × 1.5–1.6 mm, glabrous; columella 1.4–1.7 mm. |
Seeds | gray or tan with dark brown mottling, ovoid, bluntly 3–4-angled in cross section, 1.8–2.1 × 1.2–1.4 mm, smooth to rugose. |
narrowly pyramidal-ovoid, 4-angled in cross section, 1.3–1.5 × 0.6–0.7 mm, with very faint transverse ridges or wrinkles. |
Cyathia | solitary at distal nodes; peduncle 0.9–3 mm. |
solitary at distal nodes; peduncle 0.9–1.5 mm. |
Euphorbia cordifolia |
Euphorbia golondrina |
|
Phenology | Flowering and fruiting summer–fall. | Flowering and fruiting late spring–fall. |
Habitat | Xeric oak-pine scrub, pine-barrens, sand barrens, sandy stream banks. | Deep, sandy riverbanks. |
Elevation | 0–200 m. (0–700 ft.) | 600 m. (2000 ft.) |
Distribution |
AL; AR; FL; GA; LA; MS; NC; OK; SC; TX
|
TX; Mexico (Chihuahua, Coahuila) |
Discussion | Euphorbia cordifolia is easily identified by its cordate to rounded leaf base and distinctive filiform stipules. (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.) |
Source | FNA vol. 12, p. 265. | FNA vol. 12, p. 269. |
Parent taxa | Euphorbiaceae > Euphorbia > sect. Anisophyllum | Euphorbiaceae > Euphorbia > sect. Anisophyllum |
Sibling taxa | ||
Synonyms | Chamaesyce cordifolia | Chamaesyce golondrina |
Name authority | Elliott: Sketch. Bot. S. Carolina 2: 656. (1824) | L. C. Wheeler: Proc. Biol. Soc. Wash. 53: 8. (1940) |
Web links |