Euphorbia hirta Linnaeus, Sp. Pl.

Mugnai, Michele, Lazzaro, Lorenzo, Nuzzo, Luca Di, Foggi, Bruno, Viciani, Daniele & Ferretti, Giulio, 2021, Synopsis of Euphorbia section Anisophyllum (Euphorbiaceae) in Italy, with an insight on variation of distribution over time in Tuscany, Phytotaxa 485 (1), pp. 1-65 : 20-21

5. Euphorbia hirta Linnaeus, Sp. Pl. 1: 454. 1753.

Type (lectotype designated by Wheeler 1939: 68):—[s.l.] Herb. Linn. 630.7 ( LINN image!)

≡ Chamaesyce hirta (L.) Millspaugh (1909: 303)

≡ Euphorbia pilulifera var. hirta (L.) Thell. in Graebner (1917: 425)

= Euphorbia globulifera Kunth in Humboldt et al. (1817: 56). Type (lectotype, designated by Wheeler 1939):— VENEZUELA. Cumana s.d., A.J.A. Bonpland & F.W.H.A. von Humboldt 403 (P00669824 image!; isolectotype fragment F0056640F image!)

Description:—Herbs, annual or perennial, with taproot. Stems erect to ascending, rarely prostrate, 10–50(–75) cm, usually both strigillose and hirsute. Leaves opposite; stipules usually distinct, rarely connate at base, undivided or divided into 2–4 linear-subulate segments, 0.5–1.8(–2.9) mm, pilose, often with glands at base; petiole 1–3 mm, usually both strigillose and hirsute; blade ovate to rhombic, 7–43 × 3–18 mm, base strongly asymmetric, margins serrulate to double serrulate, apex acute, surfaces often with reddish spot, usually strigose to hirtellous; 3–5-veined from base. Cyathia in dense, axillary and terminal, capitate glomerules, with reduced, bractlike leaves subtending cyathia, axillary glomerules either sessile or at tips of elongated, leafless stalks; peduncle 0.4–2.1 mm. Involucre obconic, 0.6–1.2 × 0.4–0.9 mm, strigillose; glands 4, greenish to pink, circular, oblong, or reniform, 0.1–0.2 × 0.1–0.2 mm; appendages white to pink, flabellate or oblong, (0–)0.1–0.6 × (0–) 0.1–0.7 mm, distal margin usually entire. Staminate flowers 2–8. Pistillate flowers: ovary strigillose to canescent; styles 0.2–0.6 mm, 2-fid 1/2 length. Capsules subglobose to slightly oblate, 1.0–1.3 × 1.1–1.6 mm, strigillose; columella 0.7–1.0 mm. Seeds brownish red to orange or pink, narrowly ovoid, 4-angled in cross section, 0.7–0.9 × 0.5–0.7 mm, usually rugulose or with 3–6 low transverse ridges, rarely nearly smooth.

Iconography:— Jercinovic (2007: pl. 11, under the name Chamaesyce hirta ), Fig. 12.

Chromosome number:—2n = 18 ( Wang et al. 1999); n = 9 ( Soontornchainaksaeng & Chaiyasut 1999); n = 10 (Alam 1987); n = 8 ( Keil 1976); 2n = 12, n = 9 ( Hans 1973, Trivedi et al. 1983); 2n = 20 ( Raghavan & Arora 1958).

Ecology:—Accidentally dispersed by humans, livestock and vehicles as contaminant; globally considered as weed of cereals, cotton, orchards, plantations, sunflowers, vegetables, forestry and pastures. It colonizes also disturbed areas, roadsides, vacant lots, floodplain forests and deciduous forests ( Steinmann et al. 2016).

Alien status:—Neophyte native to tropical and subtropical America, it can be considered as naturalized in Africa, Asia, Australasia and Pacific.

Occurrence in Italy:—Absent.

Taxonomic annotations:— E. hirta is similar to E. ophthalmica (see taxonomic annotations of E. ophthalmica ).