A member of a group of plants bearing distinctive juicy, acid-tasting fruits of great economic importance. The majority belong to the genus Citrus, but a few come from close relatives. All species are spiny evergreen shrubs or trees; ovoid, dark green, glossy leaves with an articulated joint at the junction of blade and stalk; the stalk often winged, sometimes to the extent of appearing as a second blade attached end-to-end to the first. The leaves of side shoots become modified to form spines. Flowers and fruits are borne on the tree at the same time; the fragrant flowers solitary or in small clusters in the axils of the leaves, with 4–5 sepals and 4–8 white fleshy petals. The fruit is a type of berry, in which the carpels (the familiar segments containing the seeds or pips buried in a pulpy flesh composed of specialized hair-cells) are enclosed in a thick, leathery rind. Both the foliage and rind of the fruit have numerous glands containing aromatic essential oils.