nucleus deposited in the embryo sac by the pollen tube moves to the center and unites with the fusion nucleus. The zygote will develop into an embryonic plant within the ovule. Union of the fusion nucleus with the second male nucleus stimulates the formation of a new tissue the endosperm. In which, food materials are stored as development of the ovule proceeds.

Union of one nucleus with the egg, and the second nucleus with the fusion nucleus is called double fertilization. As far as we know, double fertilization occurs only in flowering plants. After double fertilization, the ovule increases in size rapidly as a result of the formation of endosperm tissue by mitosis and the development of the new embryo. The embryo consists of one or more cotyledons.
The cotyledons develops by utilizing the food stored in endosperm. The cotyledons of some flowering plants, beans for example, digest, absorb, and store the foods from the endosperm as the ovule is maturing into a seed. As a consequence, the cotyledons become greatly enlarged because of stored food and the endosperm disappears more or less completely. Many other flowering plants (such as corn or castor), the endosperm tissue continues to grow as the ovule matures into a seed. After fertilisation, the zygote divides several times to form an embryo within the ovule. The ovule develops a tough coat and is generally converted into a seed. The ovary grows rapidly and ripens to form the fruit. Meanwhile SCERT the other floral parts may shrivel and fall of.