(1) The pollen grains of a tobacco variety-yellow orinoco-were tested about the longevity on their fertilizing power as well as the decreasing their vitality, by means of pollination test on the pistils. The pollen grains tested were previously stored under different conditions, in detail, some of them were set under ordinal room condition, keeping in Petri-dishes (wet condition), and others under absolutely dry condition, keeping in a CaCl2 desiccator (dry condition). (2) For the longer hours the pollen grains were stored, the smaller capsules were obtained by these pollen grains, and less number of seed was counted in each capsule. Practically, it may be said that the maximum duration of the fertilizing power of the tobacco pollen is 40 days under the "Wet condition", and 180 days under the "Dry condition". Moreover, in the case of smearing with the stored pollen, which had passed the periods above mentioned, the ovaries developed often into seed-less fruits. (3) The stored pollen was sown on the artificial medium (10% water solutiqn of cane sugar), and compared their germinating percentage with the fertilzing power. (4) As it is well known, the germinating percentage decreased as the pollen became older, and the ferilizing percentage also decreased in the same manner. But there were sorne differences observed between these two caases. Namely, the decrease of the former was rapid than that of the latter. In other words, the pollen which could fertilize the egg was often un-able to germinate on the media. (5) It is sometimes reported that the pollen, stored under dry condition, germinates better in the case of pretreatment keeping them in a moist chamber for a short time, than in the ordinal case of setting them directly upon the medium. In this study, the author hold the dry stored pollen grains in a moist chamber for 30 minutes to make them absorb the moisture, and set them on the media as well as on the pistils. The germinating percentage on the media increased by means of this pretreatment, but the pollen which passed the practical storing period or the dead pollen could not germinate even if such treatment, above mentioned, was made. In the case of the pollination was made upon the pistil, the effect on this pretreatment can be observed neither on the fertilizing percentage nor on the longevity of fergilizing power. (6) The relation between the length of storing of pollen and the nature of the offspring was studied. The size of the seed obtained by the stored pollen was various. Generally, they were smaller and lighter than the normal seed obtained by the fresh pollen, showing to be only two third the weight of the ordinal seed. (7) As the storing of the pollen used became longer, the vital force of the seed obtained by these pollen become smaller. Namely, it was observed that the germinating power and the germinating percentage become lower (8) In the nursery, various malformations were observed, when the seeds obtained by stored pollen were sown. These abnormality recovered gradually, but in the case of very old pollen used, the abnormality rather increased as the plants grew. mentioned, the ovaries developed often into seed-less fruits. (3) The stored pollen was sown on the artificial medium (10% water solutiqn of cane sugar), and compared their germinating percentage with the fertilzing power. (4) As it is well known, the germinating percentage decreased as the pollen became older, and the ferilizing percentage also decreased in the same manner. But there were sorne differences observed between these two caases. Namely, the decrease of the former was rapid than that of the latter. In other words, the pollen which could fertilize the egg was often un-able to germinate on the media. [the rest omitted]