what are endosperm? what are it's characteristics? and how does it looks like?

Endosperm is the tissue produced inside theseeds of most flowering plants around the time of fertilization. It surrounds the embryo and provides nutrition in the form of starch.It can also contain oils and protein.

Characteristics of endosperm:

Endosperm cells are triploid (having three sets of chromosomes); they contain food reserves such as starch, fat, and protein that are utilized by the developing seedling. It looks like a sac like structure filled with food.