In the development of angiosperms the embryo grows in the ovary. It develops after the development of the endosperm because the endosperm provides nutrition to the embryo. You are right when you say that the embryo produces in the ovary. If you remember, pollen from the anther will get stuck to the stigma due to pollinators such as hummingbirds and bees. Pollen is made of a tube cell and a generative cell. The tube cell burrows down into a pollen tube from the stigma and travel down towards the uppermost end of the ovary. The generative cell will divide to form two sperm cells. These two sperm cells will come in contact with an ovule in the ovary, which can then develop into a seed.
