The Two Phases of Sporophyte Development
These plants are therefore the “dominant” forms of the continental flora. Although they include a few species which have “gone back” to aquatic medium, most of them live on the ground and in the air, a medium often unfavourable to life. So it is not surprising to see that all these plants use more or less sophisticated means to avoid problems of the medium to the first stages of their sporophyte development. This development can be divided into two phases: first, a phase of embryogenesis, similar to that found in animals, during which the original zygote segments and proliferation builds the first organs of the young sporophyte. Incapable of living alone during this period, the embryonic sporophyte is a parasite of the organism on which it was born; it is said to have an heterotrophic life.