9. Citrus ×limon (Linnaeus) Osbeck, Reis Ostindien China. 250. 1765.
柠檬 ning meng
Citrus medica Linnaeus var. limon Linnaeus, Sp. Pl. 2: 782. 1753; C. ×aurantium Linnaeus subsp. bergamia (Risso) Engler; C. ×aurantium var. bergamia (Risso) Brandis; C. ×aurantium var. mellarosa (Risso) Engler; C. ×bergamia Risso; C. ×bergamia subsp. mellarosa (Risso) Rivera et al.; C. ×bergamota Rafinesque; C. ×limodulcis Rivera et al.; C. ×limonum Risso; C. medica Linnaeus f. limon (Linnaeus) Hiroe; C. medica subsp. limonum (Risso) J. D. Hooker; C. medica var. limonum (Risso) Brandis; C. ×mellarosa Risso; C. ×meyeri Yu. Tanaka; Limon ×vulgaris Ferrarius ex Miller (1754), not C. ×vulgaris Risso (1813).
Small trees. Branches ± spiny. Young leaves and flower buds reddish purple. Leaf blade ovate to elliptic, 8-14 × 4-6 cm, margin conspicuously crenulate, apex usually mucronate. Flowers solitary or several in fascicles. Flowers bisexual or male by ± complete abortion of pistil. Calyx cup-shaped; lobes 4 or 5. Petals 1.5-2 cm, outside purplish, inside white. Stamens 20-25 or more. Ovary subcylindric or barrel-shaped; stigma clavate. Fruit yellow, ellipsoid to ovoid, narrowed at both ends, surface usually coarse and lemon scented, apex usually with a mammilla; pericarp thick, difficult to remove; sarcocarp in 8-11 segments, pale yellow, acidic. Seeds ovoid, small, apex acute; seed coat smooth; embryo usually solitary but sometimes numerous; cotyledons milky white. Fl. Apr-May, fr. Sep-Nov. 2n = 18, 36.
Cultivated and sometimes naturalized in S China.
The parents of the lemon are Citrus ×aurantium and C. medica. Backcrosses with either parent give a range of sour to sweet lemons which go under various names and perhaps would best be considered as forming cultivar groups, e.g., Bergamot Group. The rough lemon, C. ×taitensis Risso (C. ×aurantium subsp. jambhiri Engler; C. ×jambhiri Lushington; C. ×sinensis subsp. jambhiri (Lushington) Engler), sometimes included here, is perhaps C. medica × C. reticulata.
The name "Citrus limonia" has been misapplied to other Citrus taxa.