Are there really always ten segments in an orange?

The flower of the orange tree has five-fold symmetry, and each ovary divides into two parts. These halves then develop into segments, resulting in a total of ten.

However, in some fruits, the segments may further divide, and usually one of the new segments turns out to be significantly smaller than the other.

Additionally, in 'navel' varieties, there may be several very small segments at the top of the fruit, representing a rudimentary second fruit inside the main one.