The vegetative organs of flowering plants are the root, the stem, and the leaf, which develop from the fertilised egg cell, the zygote. The germ or embryo, consisting of one or more cotyledons, the embryonic stem forming the shoot system, and the radicle forming the root system, develops from the zygote through a series of cell divisions. In ferns, the sexual organs appear on the prothallus that develops from the spore, and after the fertilisation of the egg cell, the fern embryo developing from the zygote begins to develop in the female sexual organ. The embryo develops into a new plant without a dormant state, while the prothallus and the root primordia of the embryo die off and are replaced by roots of shoot origin.