The endocarp is the innermost region of the pericarp, the wall of a fruit. It lies inward of the mesocarp and surrounds the space containing the seeds. In a drupe such as a peach, the endocarp hardens into the stone.[ref]
The prefix specifies position, not one universal material. A hard endocarp is characteristic of a drupe, but naming an inner fruit-wall layer does not require every fruit to possess a stone. Following the tissue from the ovary into the mature fruit distinguishes endocarp from the seed coat inside it.
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