1. Ocimum basilicum L. (basil, sweet basil, lemon basil)

Pl. 438 g–i; Map 1975

Plants annual, with taproots. Stems 20–70 cm long, erect or ascending, bluntly to sharply 4-angled, several- to many-branched, moderately pubescent with short, downward-curved, hairs, sometimes nearly glabrous toward the base. Leaves opposite, short- to long-petiolate, the petioles usually winged, at least toward the tip, with a characteristic, pungent odor when bruised or crushed. Leaf blades 1–7 cm long, ovate to narrowly ovate or elliptic, unlobed, the margins entire or with relatively sparse, fine, blunt teeth, angled to more commonly tapered at the base, angled or tapered to a bluntly or sharply pointed tip, the surfaces glabrous or sparsely short-hairy along the main veins, the undersurface also with conspicuous sessile glands. Inflorescences terminal, of slender, elongate spikelike racemes, the flowers 6 per node, these short-stalked. Bracts 5–8 mm long, shorter than to about as long as the flowers, ovate to lanceolate or elliptic, sharply pointed but not spinescent; bractlets absent. Calyces 3.5–4.0 mm long at flowering, strongly zygomorphic, slightly asymmetric at the base, more or less bell-shaped, the tube more or less 15-nerved (the upper lip with a dense network of veins, hairy in the mouth, 5-lobed, the lobes mostly shorter than the tube, the upper lobe enlarged, with the margins extending downward along the tube as a pair of crests, the whole structure depressed-ovate to circular, appearing as a raised flap or circular cap of tissue, the 2 lateral lobes broader and slightly shorter than the 2 lower lobes, these all narrowly ovate to ovate or triangular, tapered to sharply pointed, but not spinescent tips, sparsely short-hairy and usually also with sessile glands, becoming enlarged to 7–9 mm and papery at fruiting. Corollas 6–12 mm long, zygomorphic, 2-lipped, white to pink, sometimes purplish-tinged toward the throat or toward the middle of the lower lip, the outer surface sparsely to moderately hairy, more or less bell-shaped, the tube usually shorter than the lips, hairy in the throat, the upper lip 4-lobed, the lobes arched upward, somewhat irregular along the margins, the lower lip longer than the upper lip, unlobed, obovate, somewhat finely corrugated longitudinally, spreading. Stamens 4, exserted (arched along the lower lip), the lower pair slightly longer than the upper pair, the anthers small, the connective short, the pollen sacs 2, slightly angled to nearly parallel, usually white. Ovary deeply lobed, the style appearing more or less basal from a deep apical notch. Style exserted, with 2 more or less equal branches at the tip. Fruits dry schizocarps, separating into usually 4 nutlets, these 2.0–2.5 mm long, obovoid to oblong-obovoid, rounded at the tip, the surface dark brown to black, finely wrinkled, glabrous, but often with a lacquerlike irregular covering (becoming sticky when moistened). 2n=48. August–September.

Introduced, known thus far only from the city of St. Louis (native of Asia, Africa; introduced sporadically in the eastern U.S. west to Missouri and Louisiana, also Arizona). Railroads.

Basil is a common herb used as a flavorant in various foods. The species also yields an essential oil used in perfumes and beverages (Steyermark, 1963). A number of cultivars are commonly cultivated. In its native range, O. basilicum sometimes is divided into two or more varieties. The introduced plants appear to correspond to var. basilicum, but the infraspecific taxonomy requires further study.