Abstract
The non-ripened grains contain two kinds of grains, viz., non-fertilized grains and imperfectly ripened grains (which have abortive kernles), and a method for predicting non-fertilized grains just after anthesis has already been reported by the same authors (Vol. 28, No. 4), so they have studied here the occurrence of abortive kernels which are determined at the early ripening stage and a method for predicting them. The results may be summarized as follows. 1. As a result of having studied the ripening process by classifying grains with specific gravity, the authors have found that there are two peaks in the distribution of specific gravity of grains, viz., the one is lower than 0.84 and the other is higher than 1.04 specific gravity, and very few grains distribute between the two peaks, and also the number of grains which are lower than 0.84 specific gravity is quite influential in determining the percentage of ripened grains. 2. Having classified the grains lower than 0.84 specific gravity into 7 classes according to the size of their caryopses and traced up their ripening processes, the authors have found that the grains belonging to the classes I to IV (which have small caryopses) can be discriminated from the other grains as abortive kernels which occur at the early ripening stage (cf. Fig. 2). 3. Abortive kernels begin to occur at the time at which the starch-content in culms attains its minimum, and, according to the criterion established by the authors, the time can also be expressed as 10 in the ripening grade of the panicle or the hill. (cf. Vol. 29, No. 4). 4. The percentage of abortive kernels which cccur at the early ripening stage on the central primary rachis -branch, which is located at the center on the axis of a panicle, can always represent the percentage of the whole panicle. 5. From the results obtained in the present experiment it has been made clear that the abortive kernels which occur at the early ripening stage can be discriminated from those which occur at the late ripening stage and the former can easily be predicted much earlier than the latter can be done.
