In the present study, upland cotton, variety "Kanno No. 1" was grown in pot culture. Making a distinction between the two stages of growth, namely before and after the first flowering, plants were grown in the glass house and/or in the outdoor and their growth was investigated. Accordingly, as an experimental method, nine treatments were provided as follows: (1) Plants were grown in the glass house continuously. (2) Plants were grown in the glass house until the first flowering, and after that time they were moved to the outdoor. (3) Plants were grown in the outdoor until the first flowering, and after that time they were moved to the glass house. (4) Plants were grown in the outdoor continuously. (5) Plants were sown on June 6, one month later than the other plots, and were grown outdoors continuously. (6)∼(9) Plants were treated as in (1), (2), (3), and (4) respectively, except such a treatment as that squares (flower buds) were cut off sucessively until the time of first square emergence in the plot of late sowing which showed retarded flowering. The elongation of main stem, the increase in number of main stem nodes, the development of branches, and the increase in dry weight of plant were investigated in these nine plots. Considering from these investgations, the glass house condition was better for the cotton growth than the outdoor condition, and at the same time the late sowing was better for the cotton growth than the control except for the increase in number of main stem nodes. The plants grown in the glass house from the sowing or after the first flowering had a period of interruption for about two weeks of boll setting. Therefore, in the behaviour of boll opening observed every week, the plants grown in the glass house from the sowing the first flowering showed two peaks in the frequency of boll opening through ripening period, while the plants grown outdoors from the sowing or after the first flowering showed one peak in the frequency of boll opening for the same period. Considering the influence of temperature on the yield of seed cotton, the investigations in relation to the yield of seed cotton before the interruption of bolls opening frequency which was brought by the interruption of boll setting frequency above described, were carried out in this experiment. In both of the number of bolls and the weight of seed cotton per plant, the plants grown in the glass house before the first flowering were superior to the one grown in the outdoor before the first flowering, while after the first flowering the plants grown in the outdoor were superior to the one grown in the glass house; and as far as the earliness of the first flowering concerned, the later the first flowering the better the result. In the weight of seed cotton per boll, the number of seeds per boll, and the lint percentage, the plants grown in the outdoor from sowing to maturity were superior to the one grown in the glass house before and/or after the first flowering; and as far as the earliness of the first flowering concerned, the earlier the first flowering the better the result. In the average seed weight, the plants grownin the glass house from sowing to maturity were superior to thc one grown in the outdoor before and/or after the first flowering; and as far as the earliness of first flowering concerned, the later the first flowering the better the result. In the present study, it is found that the vegetative growth becomes active and the number of bolls per plant increases in rather high temperature, but after the first flowering the setting and developmnt, of boll are better in rather low temperature.
