10. Spinacia Linnaeus, Sp. Pl. 2: 1027. 1753; Gen. Pl. ed. 5, 452. 1754.
Spinach [Latin spina, spine, in reference to spiny fruit, or Persian ispanakh, spinach]
Leila M. Shultz
Herbs, annual or biennial, monoecious, glabrous. Stems erect, not branched, not jointed, not armed, not fleshy. Leaves basal or alternate, petiolate; blade triangular-hastate to ovate, sometimes with elongated lobes, margins entire or dentate, apex acute. Inflorescences: pistillate flowers sessile in leaf axils; staminate flowers in dense terminal spikes. Flowers unisexual, rarely bisexual; staminate flowers with perianth segments 4-5, stamens 4-5; pistillate flowers enclosed by 2 accrescent or connate bracts, perianth absent, stigmas 4-5. Fruiting structures enlarged and hardened bracteoles enclosing achenes; pericarp adherent. Seeds vertical, seed coat dark, spiny or smooth; hardened bracteoles serving as seed coat; embryo annular; perisperm copious. x = 6.
Species 3 (1 in the flora): introduced; Eurasia.
The chromosome base number of six is unusual in the Chenopodiaceae. B. L. Turner (1994b) suggested that members with a base of nine, the most common number in the family, may be derived.