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FNA | Family List | FNA Vol. 12 | Euphorbiaceae

83. Euphorbia stictospora Engelmann in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 187. 1859.

Mat or narrow-seeded spurge, slimseed sandmat Mat or narrow-seeded spurge, slimseed sandmat

Chamaesyce stictospora (Engelmann) Small

Herbs, annual, with taproot. Stems prostrate, often mat-forming, occasionally with ascending tips, 5–45 cm, densely and evenly pilose to lanate. Leaves opposite; stipules distinct or connate basally on one side of stem, entire or irregularly toothed or fringed, 0.5–1.2 mm, pilose to lanate; petiole 0.3–1.5 mm, pilose to lanate; blade usually oblong to oblong-obovate, occasionally nearly circular, 3–10(–15) × 2–5(–10) mm, base asymmetric, one side usually angled or rounded and other truncate-auriculate, margins minutely or conspicuously serrulate at least toward apex, apex usually broadly rounded to broadly acute, occasionally emarginate, abaxial surface often ± lighter green and without reddish spot, both surfaces sparsely to moderately pilose to lanate; 3-veined from base or venation obscure. Cyathia solitary at leaf nodes or in small, cymose clusters on congested, axillary branches; peduncle 0.7–2.5 mm. Involucre obconic, 0.7–1 × 0.4–0.6 mm, moderately to densely pilose to lanate; glands 4, reddish, ± unequal, oblong, 0.1 × 0.1–0.3 mm; appendages white to strongly pinkish or reddish tinged, often unequal, sometimes 1 to all absent, 0–0.3 × 0–0.4 mm, 3-lobed or rudimentarily 1-lobed, distal margin crenate. Staminate flowers 3–9. Pistillate flowers: ovary pilose to villous, hairs occasionally slightly appressed; styles 0.2–0.5 mm, unbranched or inconspicuously notched at tip. Capsules ovoid, 1.6–2.3 × 1.4–1.5 mm, moderately to densely villous with hairs usually slightly appressed, pubescence often concentrated on proximal 1/2 or along lobes; columella 1.5–2 mm. Seeds light to dark brown, usually mottled, sometimes with thin, white coating, often wearing away irregularly, narrowly oblong-ovoid to ellipsoid, 3–4-angled in cross section, 1–1.5 × 0.5–0.6 mm, with short, irregularly interrupted furrows, appearing partially and irregularly few-ridged.

Flowering and fruiting midsummer–early fall. Open disturbed areas, rocky slopes; 100–2100 m; Ariz., Colo., Iowa, Kans., Mo., Nebr., N.Mex., N.Dak., Okla., S.Dak., Tex., Wyo.; Mexico (Chihuahua, Durango, San Luis Potosí).

Euphorbia stictospora has been recorded from New York, but this disjunct occurrence likely represents a waif or misidentification.


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