We saw in the previous chapter that it is characteristic for morphogenetic events to continue throughout the life-span of most plants. This is in marked contrast to animal development, in which there is a concentration of morphogenetic phenomena in the embryonic stages. Nonetheless, like the animal, the vascular plant begins life as a single cell, the fertilized egg, and passes through an embryonic phase during which the fundamental body plan is laid down. Although it may be argued that all plants that develop from a single cell into a multicellular state pass through an embryonic phase, historically the term embryo has been restricted to those groups in which the early stages are enclosed within parental tissue and are presumed to be nutritionally dependent upon the parent organism. On this basis the bryophytes and the vascular plants often are designated the Embryophyta. In the bryophytes and the lower vascular plants there is no interruption of growth to mark the end of the embryonic phase, which is therefore rather ill defined. On the other hand, in the seed plants, embryonic development is considered to be terminated at the maturation of the seed, and this leads to a sharp distinction between the embryo and all postgermination stages.

Throughout the Embryophyta, as well as in some lower groups, plant development from a zygote alternates in the life cycle with development of a second plant body from a single-celled spore.