Abstract: In the literature, the information on the correlation between the material changes and the cold resistance of plants is full of contraditions, especially in regard to the changes of the sugar and protein contents in connection with the development of the cold resistance in hardened condition. The present work was undertaken with an attempt to study the changes of the intracellular materials of wheat in the overwintering period with cytochemical methods. The wheat varieties used in this study were the same as used in our previous work (Chien and Wu, 1965), these are, 2 winter varieties (Nungta 183 and Huapei 187), 2 spring varieties (Nanta 2419 and Piyü), and 2 intermediate ones (Pima No. 1 and Pingyaian 50). The plants of the different varieties were cultivated under the same environmental conditions. Samples were collected and fixed at the same time (twice a month from October to March). For making microscopical preparations, the sections of materials for comparative studies were mounted on the same slide, so that they all were subjected to exactly the same treatment. The results obtained are summarized as follows: 1. The starch content in the cells of the tillering nodes increased, as the temperature fell in autumn. The starch grains gradually disintegrated when the plants came in hardened period (late October to mid-November), and completely disappeared in severe winter (January). They were regenerated in mid-February. 2. The soluble sugar gradually increased with the falling of the temperature in late autumn and steadily increased until the temperature approached 0 ℃. However, when the temperature dropped further, the soluble sugar content decreased and finally in March reached the level which it assumed before winter. 3. It was determined by cytochemical reactions that the cytoplasmic proteins and RNA and the nuclear basic proteins increased from late autumn to early winter. The degree of these changes showed apparent difference between the different varieties. Based on the phenomena observed, the authors discussed their correlation with the cold resistance of wheat plants. 4. The fat and lipids were also tested, but there was no indication of the occurrence of these substances in the winter season. The study on the DNA content revealed no correlation of any kind with the development of the wheat hardiness.