The time intervening between pollination and fertilization was investigated with both self-pollinated and cross-pollinated flowers. In cross-pollination the parents were separate plants. This point was investigated with plants out of doors during the summer of 1916 and with plants in the greenhouse during the following winter. The time elapsing between pollination and fertilization ranged from 50 to 55 hours and was not longer in the case of self-pollinated than with cross-pollinated flowers. Furthermore, the rate of the development of the embryo in each kind of pollination was studied and was found to be as rapid in self-pollination as in cross-pollination. Therefore, self-pollination is apparently as effective as cross-pollination in _Melilotus alba_ so far as the vigor of pollen tubes and the rate at which embryos develop are concerned. _Melilotus officinalis_ was not studied in reference to this point. Considerable difference often exists in the size of the young embryos in the ovules of the same pod. This is due in part to a difference in the time of fertilization, although some of it is due to a difference in nourishment. It was observed that the ovule first fertilized might be an upper one, lower one, or any one between these. Occasionally one or more ovules are not fertilized. DEVELOPMENT OF THE SEED. A proembryo with a rather long suspensor is developed from the fertilized egg. (Pl. II, fig. 2). The endosperm, which quite early forms a peripheral layer around the entire embryo sac, develops most rapidly about the embryo, which soon becomes thoroughly embedded in it. (Pl. III, figs. 1 and 2.) After the embryo has used up the endosperm in the micropylar end and has enlarged so much as to occupy nearly all of the space in this region, the development of the endosperm becomes more active in the chalazal end, and when the embryo is mature there is very little endosperm left. The seed coat begins to form about the time of fertilization, although it apparently does not depend upon it, for in ovules where fertilization is prevented the outer integument undergoes the early modifications in the development of the seed coat before the ovule breaks down. The development of the seed coat is apparent first at the micropylar and chalazal ends, where the outer cells of the outer integument become much elongated and their outer walls thicken very soon after fertilization. The modifications in the development of the seed coat extend around the ovule from these points, involving at first only the outer or epidermal layer of cells which form the malpighian layer. Later, the cells just beneath the malpighian layer form the osteosclerid layer. Accompanying or closely following the formation of the osteosclerid cells, the remaining cell layers of the outer integument become modified into the nutritive and aleurone layer, and the seed coat is fully formed. Meantime the inner integument is practically all used as food. Plate I. [Illustration]