箭叶橙 jian ye cheng

Citrus auraria Michel; C. echinata Saint-Lager; C. hyalopulpa Tanaka; C. kerrii (Swingle) Tanaka; C. macroptera Montrouzier var. kerrii Swingle; C. papeda Miquel; Fortunella sagittifolia F. M. Feng & P. I Mao; Papeda rumphii Hasskarl.

Trees 3-6 m tall. Branchlets with spines. Leaves dark red when young; petiole winged, apex rounded to truncate; leaf blade ovate, 5-8 × 2.5-4.5 cm, 1-2.5 cm longer (rarely same length) and 0.5-1 cm wider than winged petiole, tertiary veins conspicuous, margin apically conspicuously and sparsely crenate, apex narrowly obtuse. Inflorescences with (1 or)3-5 flowers; peduncle 1-5 mm. Flower buds globose. Calyx lobes 4 or 5, broadly triangular, ca. 4 × 6 mm. Petals white but pinkish red outside, 7-10 mm. Stamens ca. 30; filaments distinct. Style short, thick. Fruit lemon yellow, ellipsoid to subglobose, 5-7 × 3-5 cm, slightly coarse or smooth, oil dots numerous and prominent, apex rounded; pericarp thick; sarcocarp in 11-13 segments, very acidic and slightly bitter. Seeds numerous 1.5-1.8 × 1-1.2 cm, ridged; embryo solitary; cotyledons milky white. Fl. Mar-May, fr. Nov-Dec.

N Guangxi, Yunnan [Indonesia, Myanmar, New Guinea, Philippines, Thailand].

Although apparently native to S China into SE Asia and Malesia, the natural distribution of this species is obscured by cultivation. Selected forms are cultivated throughout the warm parts of the world for their culinary (leaves) and medicinal (fruit) uses. All named taxa (save perhaps some from central Malesia) seem to have been based on cultivated plants as discussed by Mabberley (Gard. Bull. Singapore 54: 173-184. 2002). Commonly seen in China are cultivated plants (the "lime leaves" of commerce) with the following characteristics: leaf blade broadly elliptic, apex obtuse to rounded; fruit subglobose, ca. 4 × 3.5 cm, smooth, apex with a papilla; pericarp ca. 2 mm thick; sarcocarp in 6 or 7 segments, 6-8-seeded but 1 or 2 seeds undeveloped; seeds pyramidal, 1.5-1.8 × 1-1.4 cm, 0.8-1.2 mm thick, with alveolate ridges.