Abstract
To give a solution of the problems in progamic phase of test-tube pollination, native behavior of pollen tubes in an ovary was examined. The observation was mainly performed on self-pollinated ovary of Nicotiana tabacum by scanning electron microscope. For finding easily pollen tube entrance into an ovule, a new method using dark field microscope was developed. The first group of pollen tubes penetrated into ovarian cavity about 32 hr after pollination, grew down directly on the surface of placenta and reached the bottom of placenta about 38 hr after pollination. The pollen tubes penetrated later grew down on the layer of pollen tubes which had already covered the surface of placenta and entered into ovules gradually from top to bottom of the placenta. The pollen tube entrance into an ovule began about 38 hr after pollination at the top and completed in 3 rd day at the bottom of placenta. Thus, ' it was cleared that a great deal of pollen tube more than all of ovules on a placenta and the order on behavior of pollen tubes are required for the pollen tube entrance into an ovule. These conditions in ile vivo progarnic phase may be important also in the case of test-tube pollination.
