The fruit of citrus is called a hesperidium. The exocarp, colored yellow, orange, or green, is called the flavedo. Located in the exocarp are spherical oil glands containing, e.g., lemon oil. The white portion of the fruit wall is the mesocarp and is called albedo. The locule is an air-filled chamber in which the future seeds, the ovules, are found. In the hesperidium, the layer of endocarp lining the outside of the locule grow as hairs that project into the locule. Cells of these hairs store water, organic acids, and sugars, and each hair therefore becomes a juice sacs. These juice sacs eventually fill the locule. The locule, when mature, becomes the section of a tangerine containing the juice sacs (hairs) within.
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