The ovule of an angiosperm is technically equivalent to the seed of a gymnosperm. Both structures contain a megasporangium, which is the structure that produces the female gametophyte, as well as an integument, which is a protective layer that surrounds the megasporangium. The key difference between the two structures is that the ovule of an angiosperm is enclosed within an ovary, which is a specialized structure that contains and protects the developing ovule and eventually becomes the fruit of the plant, while the seed of a gymnosperm is not enclosed within an ovary and is exposed to the environment.