Navel orange

The navel orange is a variety of orange with a characteristic second fruit at the apex, which protrudes slightly like a human navel. This variety first was caused by a mutation in an orange tree, and first appeared in the early 19th century at a monastery in Bahia, Brazil. The mutation caused the orange to develop a second fruit at its base, opposite the stem, embedded within the peel of the primary orange. This mutation also caused it to be seedless, meaning the only way the plant can be propagated is by cutting and grafting. Navel oranges are mainly an eating fruit because they are seedless and their thicker skin makes them easy to peel. They are also less suitable for juice than other orange varieties as they are less juicy, and because their flesh contains limonin, which becomes bitter when exposed to air.