Citrus hystrix - Kaffir lime

The Kaffir lime is a dwarf tree or shrub with thorny branches. The leaf stalks are strongly broadened ("winged"), giving the impression of two joined together in the longitudinal direction. The leaves themselfes are covered with a very glossy layer of wax. 
From the white, relatively small flowers pear-shaped fruits develop that are typically only 6 cm (2 inches) in size. The uneven, rough shell turns from dark green to yellow as the fruit ripens. However, Kaffir lime fruits are almost always immature, so are traded whilst green.