Citron

Citrus medica L. Sp. PI. 782. 1753
Citrus tuberosa Mill. Gard. Diet. ed. 8. 1768.
A glabrous shrub or small tree, 3 or 4 m. high ; branches unarmed, or armed with rather short, stout, sharp more or less horizontal thorns 1-3.5 cm. long ; petioles usually wingless ; leaves evergreen, unifoliolate ; leaflet oblong to elliptic, occasionally somewhat oblongobovate, 12-20 cm. long, 4-6 cm. broad, rounded and more or less emarginate at the apex, sometimes acutish, dull green, the margin serrulate-crenate ; flowers axillary in compact clusters of 3-10; petals oblong, white within, tinged with purple on the outside; berry usually very large, oblong to nearly globose, 12-20 cm. long, 6-15 cm. in diameter, often mamillate at the apex, smooth or coarsely wrinkled, deep-orange or bright-yellow ; rind 3-7 cm. thick ; pulp often rather dry, acid and somewhat bitterish or sweetish.
Type locality : Southern Asia.
Distribution : Widely cultivated ; thoroughly naturalized in tropical and subtropical regions.