Abstract
1. In the early stage of development the gametophyte, especially the female gametophyte, of flowering plants passes through a multinucleate stage without exception. Non-appearance of the multinucleate stage in the male gametophyte must be due to the suppression of the development of the early stage of the gametophyte generation. In the embryo formation in the gymnosperm plants and the endosperm formation in the angiosperm plants the multinucleate stage also precedes the uninucleate stage. These data show us the common presence of the genes concerning this character in these plants. The common occurrence of the genes in such a large group of plants can not be considered as due to the appearance of these genes in a later stage in their phylogeny, but is more adequate to consider that the genes were inherited through common ancestral form, of these plants :
The regression of the multinucleate stage in the development of the female gametophyte in the flowering plants, from the systematically primitive forms. to the recent ones suggests that the multinucleate stage were probably more developed among ancestral groups.
2. The gametophyte of the flowering plants is of multinucleate and of aquatic type, while the sporophyte is of uninucleate and. of terestorial type. But in their ancestral forms these two generations would have been alike, namely both were aquatic having longer anterior multinucleate, stage and rather shorter uninucleate posterior stage in their lives. In the phylogenetically later stage, in the gametophyte the anterior multinucleate stage is maintained while the posterior uninucleate stage is abridged mostly. On the contrary in the Sporophyte the anterior multinucleate stage is abridged while the posterior uninucleate stage is developed vigorously and highly differentiated; moreover the root formation a most important, and a unique mutant character has appeared in this group. By the development of the root the plant got the capacity of obtaining numerous new materials from the soil, and became possible to grow vigorously as land plant.
3. The parasitic condition of the sporophyte in the early stage of embryo development on the gametophyte had a role for obtaining the terestorial habit of the sporophyte. On the other hand the vigorous growth of the sporophyte on the soil should have led the parasitic habit of the gametophyte on the sporophyte.
4. The multinucleate condition is regarded as the original structure of the protoplast in which the differentiation of uninucleate condition has subsequently been established.
