Like other fruits, it has three layers: exocarp, mesocarp, and endocarp. The exocarp is the shiny outer skin, usually yellow-green to yellow-brown. The mesocarp consists of a thick layer of fibers called coir. The woody endocarp forms a seed, called a coconut, which contains a single seed. The endocarp is about four millimeters thick and has three characteristic germination holes (micropyles) at the distal end. Only one of them is functional, covered with a soft shell through which the germinating shoot can penetrate. The other two are encapsulated. The inner wall of the seed is lined with a thick layer of solid endosperm, which when dried is called copra.
The inside of the seed is filled with a liquid form of endosperm, called coconut water. A small cylindrical embryo is embedded in the solid endosperm, directly below the functional germination opening.
