The female reproductive structure that develops into a seed in a seed-bearing plant. An ovule consists of a megasporangium surrounded by one or two layers of tissue called integuments. The megasporangium produces spores that develop into megagametophytes. These megagametophytes remain within the tissues of the ovule and produce one or more egg cells. Sperm from pollen grains enter the ovule through an opening called a micropyle and fertilize the egg cells. The resulting embryo then begins to develop within the ovule, which becomes a seed. Among the conifers and cycads, the ovules are typically found in pairs on scales in the female cones. The ovules of angiosperms are contained in a structure called the ovary within in the flower.