抄録
1. The aim of the present study is to gain informations as to how the varieties of rice plant are to be divided into groups. More than one hundred and twenty varieties were taken out nearly randomly from numerous varieties collected from various districts of Eastern Asia, and were observed with respect to various characters. On the ground of those results, discontinuity of varietal variation, intervarietal correlations and tendencies in character combination wete investigated. 2. Besides phenol reaction which is known to be determined by a single genic change, several characters as follows which would be effected by a number of genes, i.e. potassium chlorate resistance, Iow temperature resistance, drought resistance and the length of awn, showed discontinuous intervarietal variations, and in regard to each of these characters the used varieties seemd to be divisible into two groups. The number of days of germination and the weight of grain shedding seemed to some extent to be discontinuous. The degree of destruction of endosperm by caustic potash solution (alkali-test), the number of days of endosperm maturation, the length-width ratio of unhulled grain, the length of first and second internodes grown in a dark place, showed continuous appearences of varietal variation. 3. In a gre;ater part of these characters, except the lerigth-width tatio of unhulled rice and the length of frst and second internodes, the varieties positive in phenol reaction and the negative ones showed characteristics contrary to each other. And intimate intervarietal correlations were found between these characters.
