Citrus L., Sp. Pl. 782. 1753; Gen. Pl. ed. 5: 341. 1754; Hook. f., Fl. Brit. Ind. 1: 514. 1875; Tutin et al., Fl. Eur. 2: 229. 1968; Parker, For. Fl. Punj. ed. 1: 62. 1918 (Reprint 1973); Zhang & Mabberley, Fl. China @ eFloras.org 11: 90; Fl. Pak. @ eFloras.org p. 19.

Evergreen, small trees or shrubs; young branches often flat and angled, usually with solitary or paired spines at leaf axils. Leaves alternate, simple, 1-foliate (rarely 3-foliate); petiole often winged, jointed to the base; leaf blade subleathery to leathery with dense pellucid fragrant oil dots, margin crenulate, rarely entire. Flowers bisexual or male, actinomorphic, hypogynous, solitary or clustered in axillary racemes or in small cymes, fragrant. Calyx cupulate or urceolate, glabrous or pubescent. Petals (4-) 5 (- 8), white or outside pinkish red, linear-oblong, imbricate, thick. Stamens usually 4(-10) times as many as petals; filaments free or polyadelphous (basally coherent), compressed at base. Disc cupular, annular or short. Ovary multilocular (5-18-loculed), 2-8 ovules per loculus, 2-seriate or collateral; style stout, deciduous; stigma large, capitate. Fruit a berry (hesperidium), globose to oblong to oblate, fleshy, many-celled, septa membranous, rind tight or loose, with oil glands embedded in pulpy vesicles. Seed coat smooth or ridged.

28 species

Citrus japonica Thunb., Nova Acta Regiae Soc. Sci. Upsal. 3: 208. 1780; Fl. China @ eFloras.org 11: 92.

Trees, up to 5 m tall. Branchlets numerous; spines very minute or absent. Leaves 1-foliate; petiole 7-12 mm long, narrowly winged, 1-3 mm wide; leaf blade elliptic to obovate-elliptic, 3-7 cm x 1.8-3.5 cm, base generally cuneate, rarely rounded, margin dentate near apex to upper half, basal part entire, apex acute, obtuse or emarginate. Flowers generally solitary, axillary, subsessile (pedicel ca. 1 mm long), 2.3-2.8 cm across, white, star-shaped, actinomorphic, bisexual, hypogynous fragrant. Sepals 5, connate, campanulate, ca. 3.5 mm long, greenish-yellow, gland-dotted, lobes ca. 1- 1.5 mm x 1-1.5 mm, ovate-triangular. Petals 5, free, 12-15 mm x 3.5-5 mm, oblanceolate to oblong, white, gland-dotted abaxially, glands greenish-yellow. Stamens 20, 8-10 mm long; filaments cohering into 5 bundles of 3 each, each group alternating with a single stamen inflexed towards pistil; anthers 0.75 mm long, ovoid, bithecous, dorsifixed, dehiscence longitudinal. Disk below the ovary, large, annular. Ovary +/- globose, 1.5-2 mm x 1.5-2 mm, glabrous, 7-9-locular, 3-4 ovules per loculus; style ca. 2.5 mm long; stigma capitate, +/- clavate. Fruit bright orange, globose to slightly oblate, 2-3 cm in diameter, smooth, 3-4-seeded. Seeds broadly ovoid, apex mucronate, seed coat smooth.

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