The author Studied of the chlorophyll content of barley plant, in order to find the relation to growth, and differences between the spring and winter growing habit of barley. The materials used were selected 15 varieties of typical spring and winter barley, as well as intermediate. The seeds were sown in the fall and spring of 1929 in the experiment field. Samples were collected at intervals of approximately one month from September 5th to June 6th. For the determination of chlorophyll (α+β) content, the WILLSTATTER'S colorimetric method modified by SCHERTZ was used, and the results were given either in the percentage to the fresh-or dry-weight, as well as to the definite leaf area, or to the definite volume of dry tissue powder. The chief results of the experiments may be summarlized as follows. 1) The chlorophyll content of the plant appears to related closely with the growth of barley, namely the content increases rapidly from early stages of development in September to the active growing period in October, and then decreases again gradually to December. It remains at this level until next March and begins a sharp rise in April when the new leaves start to grow. 2) Therefore, the content found to be correlated with the rate of growth. The higher the growth rate of plant is, the richer the pigment of the leaf is contained. This fact also agrees with the case of rice plant previously stated by the auther. 3) The relations existing between the content and the growing habit of barley differs more or less influenced by temperature. On a condition of mild climate in early autumn the differences do not look as marked as in severe cold in winter. Thus, the content ratio found to be: winter barley 100: intermediate barley 106: spring barley 97 on september 5th, while on January 10th the relations become 100: 96: 64 respectively. This is believed to be due to the cold resistance of these varieties of barley, because the former two are much resistant than the latter. 4) On the contrary, the chlorophyll content of winter barley seems to be less than the spring and intermediate barley under such a condition of hot early summer. For example, the ratio of content indicates: spring barley 100: intermediate barley 103: winter barley 72 on June 6th. This is probably due to the varietal differences of plant to the high temperature and high light intensity. 5) From the foregoing data, it is difficult to see a definite correlations between the chlorophyll content and the photoperiodic responces upon the barley plant. 6) There seems to be a close relation between the chlorophyll content and the cold resistance of barley, because the winter and intermediate barley which much resistant to cold, contains more chlorophyll than the latter.