An ovule is a structure found in seed plants (gymnosperms and angiosperms) that develops into a seed after fertilization of an egg-cell within it. In gymnosperms (conifers) the ovules are unprotected, being borne on the inner surface of the female cone; in angiosperms (flowering plants) the ovule is protected by the megasporophyll which forms a closed structure (carpel) within which they form singly, or in numbers. Each ovule is attached to the carpel wall by a stalk or funicle which arises from its base (chalaza). A mature angiosperm ovule consists of a central mass of tissue, the nucellus, surrounded by one or two protective layers, the integuments, from which the seed coat is ultimately formed. Integuments enclose the nucellus except at its apex, where there is a small passage, the micropyle. Within the nucellus is a large oval cell, the embryo sac developed from a megaspore, containing the naked egg-cell.