10. Citrus ×aurantium Linnaeus, Sp. Pl. 2: 782. 1753.
酸橙 suan cheng
Aurantium ×acre Miller; A. ×corniculatum Miller; A. ×distortum Miller; A. ×humile Miller; A. ×myrtifolium Descourtilz; A. ×sinense Miller; A. ×vulgare (Risso) M. Gómez; Citrus ×amara Link; C. ×aurantium subsp. amara Engler; C. ×aurantium var. bigaradia (Loiseleur) Brandis; C. ×aurantium var. crassa Risso; C. ×aurantium var. daidai Makino; C. ×aurantium var. dulcis Hayne; C. ×aurantium var. fetifera Risso; C. ×aurantium var. lusitanica Risso; C. ×aurantium var. myrtifolia Ker Gawler; C. ×aurantium subf. nobilis (Loureiro) Hiroe; C. ×aurantium var. sanguinea Engler; C. ×aurantium subf. sinensis (Linnaeus) Hiroe; C. ×aurantium subsp. sinensis (Linnaeus) Engler; C. ×aurantium var. sinensis Linnaeus; C. ×aurantium subsp. suntara Engler; C. ×aurantium var. vulgaris (Risso) Risso & Poiteau; C. ×aurata Risso; C. ×bigaradia Loiseleur; C. ×changshan-huyou Y. B. Chang; C. ×communis Poiteau & Turpin; C. decumana (Linnaeus) Linnaeus var. paradisi (Macfadyen) H. H. A. Nicholls; C. ×dulcis Persoon; C. ×florida Salisbury; C. ×humilis (Miller) Poiret; C. maxima (Burman) Merrill var. uvacarpa Merrill; C. ×myrtifolia (Ker Gawler) Rafinesque; C. ×paradisi Macfadyen; C. ×sinensis (Linnaeus) Osbeck; C. ×sinensis var. brassiliensis Tanaka; C. ×sinensis subsp. crassa (Risso) Rivera et al.; C. ×sinensis subsp. fetifera (Risso) Rivera et al.; C. ×sinensis subsp. lusitanica (Risso) Rivera et al.; C. ×sinensis var. sanguinea (En gler) Engler; C. ×sinensis var. sekkan Hayata; C. ×sinensis subsp. suntara (Engler) Engler; C. ×taiwanica Tanaka & Shimada; C. ×tangelo Ingram & H. E. Moore; C. ×vulgaris Risso.
Small trees. Branches with spines up to ca. 8 cm. Petiole obovate, 1-3 × 0.6-1.5 cm, base narrow; leaf blades dark green, thick. Inflorescences racemes, with few flowers or flowers solitary. Flowers perfect or male by ± complete abortion of pistil; buds ellipsoid to subglobose. Calyx lobes 4 or 5. Petals 2-3.5 mm in diam. Stamens 20-25, usually basally connate into bundles. Fruit orange to reddish, globose to oblate, surface coarse; pericarp thick, sometimes difficult to remove; sarcocarp with 10-13 segments, acidic and sweet or sometimes bitter. Seeds numerous, large, with ridges; embryo(s) solitary to numerous; cotyledons milky white. Fl. Apr-May, fr. Sep-Dec. 2n = 18.
Cultivated and sometimes naturalized in most of China S of the Qin Ling.
Oranges and grapefruit are Citrus maxima × C. reticulata and the backcrosses with the parental species. Many of these hybrids arose in China, although others were synthesized, especially in the U.S.A., and introduced in China. The cultivars can be arranged in groups: Sour Orange Group (the sour or bitter orange most like the original cross), Sweet Orange Group (the commercially most important being backcrosses with C. reticulata ), and Grapefruit Group (representing backcrosses with C. maxima and first being made in the Caribbean).
Sweet Orange Group
Petiole long and narrow; leaf blade ovate, ovate-elliptic, or rarely lanceolate, 6-10 × 3-5 cm or larger. Calyx lobes 3-5. Petals white or rarely purplish, 1.2-1.5 cm. Style stout; stigma large. Fruit orangish yellow to orangish red, globose, depressed globose, or ellipsoid; sarcocarp with 9-12 segments, yellow, orange, or purplish, sweet or slightly acidic. Seeds few or absent; seed coat slightly ridged; embryos numerous; cotyledons milky white. Fl. Mar-Jun, fr. Oct-Dec but some cultivars Feb-Apr. 2n = 18, 27, 36, 45.
Below 1500 m. Cultivated S of the Qin Ling, as far NW as SE Gansu and as far SW as SE Xizang.
Branches glabrous. Leaves similar to those of Citrus maxima but leaf blade smaller and narrower, midvein ciliate. Flowers smaller than those of C. maxima. Calyx lobes glabrous. Fruit yellow, depressed globose to globose, smaller than those of C. maxima; pericarp thin; sarcocarp with 12-15 segments, yellowish white or pink, tender, juicy, slightly fragrant and acidic. Seeds few or absent; embryos numerous. Fr. Oct-Nov. 2n = 18, 20, 27, 36.