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Thia investigation was designed to study the normal development of the gametophytlc generation up to and including fertilisation in the sweet potato. The material used in this experiment consisted of four seedling clonal lines of sweet potatoes, 16-3, 98, 11,-5, and 15-7, produced at the Louisiana State University Agricultural Experiment Station. Young buds and unpollinated flowers were killed, embedded in paraffin, cut at 12-30 microns, and stained. Mature flowers were pollinated, retaoved at one, four, eight, and twelve-hour intervals following pollination, treated as the above, and cut at 30 microns. Smears of pollinated flowers were used to show the germinating pollen grains and tubes. The development of the embryo sac was normal. The functional megaspore underwent three divisions to fora eight nuclei arranged in linear order. The mature embryo sac, as found in this study, was ordinarily composed of five nuclei; two synergids, egg, and two polar nuclei. The three antipodals, as a rule, degenerated soon after they were formed, but occasionally remained until after fertilisation. It was observed, in flowers pollinated with normal pollen, that the pollen grains had germinated and entered the embryo sac within three and one-half houia after pollination. Four hours elapsed between the time the pollen tube entered the embryo sac and fertilisation. The fusion of the sperni and egg and spam and one polar nucleus occurred simultaneously. The product of the latter fusion then united with the other polar nucleus to form the endosperm. There were indications that self-incompatibility factors existed in the sweet potato.