4. Amaranthus viridis L., Sp. Pl., ed. 2. 2: 1405. 1763 Type (lectotype designated by Fawcett & Rendle 1914: 131):—UNKNOWN ORIGIN. Habitat in Europa, Brasilia, Herb. Linn. No. 1117.15 (LINN!, image of the lectotype available at http://linnean-online.org/11641/). Description:— Herbs 1–7(–8) dm tall, monoecious, annual (therophyte). Stems erect, glabrous, green to brownish, branched. Leaves black-green, ovate, rhomboidal [(2.0–4.5) × (1.5–)2.0–7.0 cm], with entire (rarely undulate) margins, apex obtuse or rounded (rarely slightly emarginate) and sometimens mucronate, base usually cuneate, usually glabrous, petioled [petiole 1.5–5.0 cm long]. Synflorescences terminal, spike- or panicle-like (sometimes axillary glomerules also occur), the main florescence 3–4 cm long, green to brown, usually thin (5–7 mm in diameter). Floral bracts yellowish or greenish, ovate to lanceolate [0.5–1.0 × 0.4–0.7 mm], shorter (up to ⅓) than the perianth, acuminate, margin entire, glabrous. Staminate flowers with 3 tepals, ovate; stamens 3. Pistillate flowers with 3 tepals, ovatelanceolate or obovate-spathulate (1.2–1.5 × 0.3–0.6 mm), with rounded apex (sometimes acute), mucronate or not; stigmas (2–)3. Fruit brownish, subglobose [(1.2–)1.4–1.7(–1.9) × 1.4–1.6(–1.8) mm] as long as or slighly longer (up to ¼) than the perianth, clearly rugose, indehiscent. Seed lenticular (0.8–1.2 mm in diameter), black or brownish-black. Iconography:— Chaudhary (1998: 239, Plate. 129b), Bayón (2015: 371, Figura 64). Phenology:— Flowering time february. Habitat and elevation:— Human-made habitat, 400–600 m a.s.l. Chromosome number:— 2n = 34. Alien status:— Neophyte species native to South America, it can be considered as naturalized in Saudi Arabia (see also Chaudhary 1998). Occurrence in Saudi Arabia (Fig. 3):— Al hudud ash Shamaliyah (Osman & El-Ameid Abedin 2019), Bisha (Abbas et al. 2020), Jizan, and Taif (Abdullah et al. 2017). Taxonomic annotation:— The name Amaranthus gracilis Desf. was cited by Mandaville (2011) as synonym of A. viridis. Desfontaines’ name was widely discussed by Iamonico (2016b) who reached to the conclusion that it is a nomen ambiguum published by Desfontaines (1804) as nomen novum pro Chenopodium caudatum Jacq. The latter Jaquin’s name was proposed as nomen rejectendum by Iamonico et al. (2015). Specimina visa selecta:— SAUDI ARABIA, Jizan, human-made habitat, (coastal plain) 5–15 m a.s.l., 17 February 2021, leg. Masrhai et Al-shaye (PNUH), det. Masrhai, conf. Iamonico (RO!).

Published as part of Hassan, Walaa A., Al-Shaye, Najla A., Alghamdi, Salma, Korany, Shereen M. & Iamonico, Duilio, 2022, Taxonomic revision of the genus Amaranthus (Amaranthaceae) in Saudi Arabia, pp. 135-157 in Phytotaxa 576 (2) on page 141, DOI: 10.11646/phytotaxa.576.2.1, http://zenodo.org/record/7461280