Final answer:
The food store of the seed known as perisperm is derived from the nucellus, which is a maternal tissue in the ovule, distinct from the endosperm that originates after double fertilization.
Step-by-step explanation:
In some angiosperms, the food store of the seed is the perisperm derived from the nucellus. In contrast to the endosperm, which is a triploid tissue formed after double fertilization, the perisperm develops from the nucellus, which is diploid maternal tissue in the ovule. The role of the perisperm is similar to that of the endosperm in that it serves as a food reserve for the developing embryo. However, unlike the endosperm, which is found in all angiosperms at some point in their development, the perisperm is not as commonly observed. Angiosperm seeds can have endosperm, perisperm, or both, depending upon the species.