Catalase activity in seeds and flour of wheat varieties (16 var. of spring and winter types) was determined at the temperature, 5°∼10°, 20°and 30°C. And the thermosensitiveness of the ferment, namely the mobility of the ferment expressed by the ratio-difference between activities at lower and higher temperature. The activity at lower temperature was calculated in each variety. The results were as follows: (1) the activity, especially that at lower temperature was higher in earlier varieties than in those of later heading. (2) the thermosensitiveness of the ferment was greater in earlier varieties than in later ones. The earlier varieties (spring types) are in general more responsible to higer temperature in their growth than the later ones (winter types). Potentials e.g. the ferment in seeds of wheat varieties showed the corresponding responses to higer temperature as plants do in their growth. (3) the activity in flour was not so much correlated to the growth habit that the author found in that of seeds.