Euphorbia trachysperma


in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 189. 1859.

Common names: San Pedro River sandmat
Synonyms: Chamaesyce trachysperma (Engelmann) Millspaugh
Treatment appears in FNA Volume 12. Treatment on page 291. Mentioned on page 256.

Herbs, annual, with slender taproot. Stems erect to ascending, 10–55 cm, glabrous. Leaves opposite; stipules distinct, narrowly triangular and often divided into 3–5 subulate to filiform segments, 0.8–1.9 mm, glabrous; petiole 1.2–3.1 mm, glabrous; blade oblong, elliptic, or ovate, 12–43 × 3–14 mm, base subsymmetric to asymmetric, rounded, attenuate, or with one side hemicordate and other side rounded, margins usually serrulate, rarely entire on some leaves or portion of blade, apex obtuse to acute, surfaces often with red blotch in center, glabrous; pinnately veined, often only midvein conspicuous. Cyathia solitary at distal nodes; peduncle 1.4–2.4 mm. Involucre oblong, campanulate, or funnel-shaped, 1.5–2.6 × 1.1–2.3 mm, glabrous; glands 4, green to yellowish or tinged with red, subcircular to oblong, 0.4–0.7 × 0.5–1 mm; appendages absent or white, often forming narrow rim or oblong to ovate, 0–0.8 × 1.2 mm, distal margin entire. Staminate flowers 50–60. Pistillate flowers: ovary glabrous; styles 0.5–0.6 mm, 2-fid 1/2 length. Capsules oblate, 2.4–3.2 × 3–3.5 mm, glabrous; columella 2.3–2.5 mm. Seeds light brown, ovoid, 4-angled in cross section, abaxial keel well developed, 1.9–2.3 × 1.3–1.4 mm, finely dimpled and papillate.

Phenology: Flowering and fruiting late summer–early winter.
Habitat: Desert scrub, desert grasslands, mesquite woodlands.
Elevation: 200–1200 m.


V12 85-distribution-map.jpg

Ariz., Mexico (Baja California Sur, Sonora).


Euphorbia trachysperma may be expected in extreme southwestern New Mexico given the close proximity of some collections in southeastern Arizona.

Selected References


Lower Taxa

... more about "Euphorbia trachysperma"
Victor W. Steinmann +, Jeffery J. Morawetz +, Paul E. Berry +, Jess A. Peirson +  and Ya Yang +
Engelmann +
Anisophyllum +
San Pedro River sandmat +
Ariz. +, Mexico (Baja California Sur +  and Sonora). +
200–1200 m. +
Desert scrub, desert grasslands, mesquite woodlands. +
Flowering and fruiting late summer–early winter. +
in W. H. Emory, Rep. U.S. Mex. Bound. +
Chamaesyce trachysperma +
Euphorbia trachysperma +
Euphorbia sect. Anisophyllum +
species +