抄録
1. It has already been known that in the com-mon cabbage the inhibiting substance that prevents self-fertilization is secreted not at all or a little in the pistil of bud stage, while abundant at the flowering time, and that it is again decreased in the pistil of old flower. In the present experiments these phenomena were corroborated by examining the behavior of pollen and pollen-tube after bud-pollination and after old flower pollination.
2. The activity of incompatible pollen on the stigmas after bud-pollination was more rapid than that of compatible pollen after crossing of open flowers. The fact that immature stigma was more receptive than mature one indicates that pollen is inhibited to some extent on the mature stigma even though it is compatible.
3. The stigmas mutilated at the time of anthesis increased self-fertility. The results of mutilation experiments show that the inhibiting substance exists chiefly in the stigma at the flowering time. This fact was also confirmed by the behavior of pollen and pollen-tube after stigma shaving method.
4. The results of experiments in which the stigmas mutilated in the bud stage were applied with their own pollen at the flowering time indicated that the stigmas mutilated were superior in the percentage of pollen germination and that of emptied grains to the control. It seems probable that in these cases the inhibiting substance was not secreted by removing stigmas in the bud stage.
5. An experiment to graft stigma upon style with the aid of gelatine indicated that pollen germination and tube growth on the stigma are affected by the character of the stigma, but not at all by that of the style.
From the results of these experiments it seems that in the common cabbage the inhibiting substance is chiefly secreted in the stigma.
