Abstract
Taking the weight of fully ripened grain as 100 and converting the weights of grains sampled successively at different ripening stages into percentage-ratios and naming these percentage-ratios as "ripening grades", the authors examined what character of the grains has the highest correlation coefficient between the "ripening grades" using plants treated in various ways and degrees in ripening stages. As the result of it, following characters were pointed out to be capable of practical use, in particular the third one being suggested to be most convenient and promising, in expressing the ripening grades. 1) Specific gravity of a grain. 2) Ratio of a kernel (brown rice) weight to its hull weight of the grain. 3) Proportion of the width of a translucent area to that of the whole area in a transverse section of a kernel.
