1. The development of the embryo sac is practically the same in all species. 2. In all species the endosperm nucleus divides and the daughter nucleus in the antipodal end enters a nucellar tube or sac which penetrates the nucellus. 3. This nucellar tube or sac is apparently for the purpose of transferring food from the nucellus to the endosperm, from which it is transferred to the embryo. 4. The endosperm is of two types: the cellular in Nymphaea and Castalia, and the nuclear followed by the cellular in Brasenia purpurea and Cabomba piauhiensis. 5. The character of the endosperm in the late stages of Brasenia purpurea and Cabomba piauhiensis indicates a greater importance in germination than in the other genera. 6. The embryo of Nymphaea advena(?) originates as a spherical mass of cells and later develops a cotyledonary ridge and suspensor, while the other species develop embryos consisting of a single row of cells, from which is formed a spherical embryo supported by a suspensor. A crescent-shaped cotyle...