Final answer:
A hard seed inside fruits like cherries, plums, and peaches is commonly known as a pit or stone, which is part of the fruit's pericarp called the endocarp. These fruits are classified as stone fruits or drupes, and the formation of the fruit aids in seed dispersal.
Step-by-step explanation:
The hard seed inside a cherry, plum, peach, and similar fruits is called the endocarp, which is part of the pericarp that encloses the seed. Specifically, in common terms, this hard seed is often referred to as the pit or stone. These types of fruits in which the endocarp is hard and stone-like are generally classified as stone fruits or drupes. This contrasts with dehiscent fruits like peas, which release their seeds, versus indehiscent fruits like peaches, which rely on other processes such as decay or consumption by animals to release their seeds. Furthermore, the function of the fruit is primarily for seed dispersal, ensuring that the seeds are spread far from the mother plant to facilitate the continuation of the plant species.