Navel oranges are oranges without seeds. In the early nineteenth century an orange tree in a Brazilian orchard produced seedless fruit, while the rest of the orchard produced seeded oranges. This naturally occurring mutation gave rise to what we now refer to as the navel orange. A bud from the mutant tree was grafted onto another orange tree; the branches that resulted were then grafted onto other trees, soon creating orchards of navel orange trees. Every time you eat a navel orange, remember that it was derived from pieces of the tree that first produced the mutated fruit!