The central part of a fruit is called the "endocarp." This part surrounds the seeds and can vary in texture and toughness depending on the type of fruit. In some fruits, like peaches, the endocarp forms a hard pit, while in others, like tomatoes, it is fleshy and edible. The structure of the endocarp plays a vital role in the fruit's ability to protect and disperse seeds, contributing to the reproductive cycle of plants.