Experiment I. The author investigated the influence of the alternate cutting of the primary rachis-branch on the protein content in the brown rice and some agronomic traits using the japonica and the improved semi-dwarf, high-yielding indica varieties. The results are as follows; 1. In all varieties, "the product of the percentage of ripened grains and the weight of 1000 grains" increased by this treatment. In this occasion, the increasing rate was much higher in the improved indica varieties than in the japonica variety. 2. In all varieties, the protein content in brown rice increased by this treatment. Experiment 2. The author compared some agronomic traits between cv. Koganemochi and its mutant whose greatest characteristic was partial sterility. It was very convenient to use this for this research. 1. There was no significant difference in the heading date, the number of panicles per hill, the number of spikelets per panicle, and the culm length between the two. 2. 1000 grains weight of the mutant and the original variety was 23.9 g and 22.0 g, respectively. The percentage of ripened grains was 94.5% in the original variety and 26.8% in the mutant. 3. Grain weight and the ammount of protein content in a grain increased more rapidly after flowering in the mutant than in the original variety. 4. The percentage of the protein content in the brown rice was always higher in the mutant than in the original variety during the ripening period. The percentages of the protein content of the mutant and the original varicty at the time of maturity were 10.56% and 7.33%, respectively. From the results of these experimcnts, it was assumed that the percentage of the protein content in brown rice became higher by the limitting of the number of the ripening grains per panicle under no restriction of dry matter production in rice plant.