抄録
It was mentioned in the previous paper on the basis of the investigation on pollen density in the air in May 1971, that pollen dispersal of larch was more vigorous under the condion of higher temperature and lower relative humidity, and that the dispersal from a stand to others in some distances was smaller than expected. The germination test of the seed lots obtained from these stands in the autumn of 1971 shows that the germination percentage is higher in the stands of higher pollen density while lower in those of lower density. The records of the flower density in the crowns and seed germination of all or several trees within a stand and the number of pollen grains caught by traps settled at different heights in the same stand, for the period from 1968 till 1972, were also compared (Fig.2 and 3). According to this comparison. the dispersal of pollen within a stand is restricted in rather narrow range ; and consequently the frequency of crossing of a tree seems to be the highest between it and the contiguous trees while reducing rapidly between it and the second, third and further. The direction of prevailing or constant wind also seeme to give a large influence on this frequency. In another pollination test with various amounts, the injection of 20mg of pollen into an isolation bag showed a pollen density of 2477 (represented by the number on 1cm^2 of slide) which was nearly the same as that caught by tie trap (2359/cm^2) in the year of the highest germination percentage. Any larger amount may not be necessary for the artificial pollination.
