The epicarp is thin and tough, the endocarp is thick and woody while the mesocarp layer is very thick and fibrous. The white endosperm does not fill the seed, but encloses a large cavity that also contains the coconut 'milk'. The flowers open and continues until the style withers. They are outgrowths of the endocarp walls and each mature sac is a living cell filled with the juice. Common sweet oranges usually have ten, two- seeded locules, each equalling a carpel.
Navel oranges are a seedless variety of oranges and classed as parthenocarpic fruit.
Seed may be produced or more usually, develop the berry parthenocarpically. Both the seeded and the parthenocarpic berry are very similar in structure when flowering. The parthenocarpic fruit is formed by the ovules degenerating, the locules become filled with a pulp rich in starch originating from the pericarp and the partitions. The seeded variety of the berry has mature seeds that almost fill the locules, with much pulp being produced. In the parenchyma of the pericarp are vertical vascular bundles.