Abstract: The accumulation and redistribution of dry matter in 11 varieties of rice from the time of flowering to harvest were studied. The dry weights of the ear and the internodes were compared in both normal and treated plants—partially or wholly defoliated or with half of spikelets removed at the time of flowering. The main results can be summarized as follows. In all the varieties there was a great increase in the dry weight of the ear from flowering to maturation. Generally about 1/4 to 1/3 of the increase was found to come from the reserve substances of leaves and stem. Since translocation from root and between the tillers was probably negligible, the great majority of dry substance (2/3–3/4) of the ear must come from concurrent photosynthesis. The magnitude of the post-flowering photosynthesis differed greatly in the different varieties, as well as under different conditions of cultivation. The loss of dry weight in the stem after flowering was different among the varieties. Some actually showed a net gain. But in general the loss was around 20%–30% of the stem weight. This loss was not equally borne between the internodes. The lowest (oldest) internodes lost the most, amounting sometimes to 1/2 of the original weights. This phenomenon was shown to be coincident with the tendency to lodge. The loss from the stem showed a definite time course. It was most rapid up to the time of milk-ripe stage. The stem weight remains low till wax-ripe when it recovered slightly and gradually went down again. The time sequence fitted well with the changing activities of the ear. Early experiments showed that respiration, enzymic activities and the accumulation of dry matter in the ear were highest in the milk-ripe stage. This correlation indicated an active transport during that period toward the ripening ear. The plants defoliated at the time of flowering yielded a smaller final total weight (ear + stem) than the intact plants (less 22%–36%), showing that the leaves were the chief assimilating organ, and their removal invariably reduced the yield. But as the total weight of the defoliated plants did show in general an increase after flowering, the stem and ear were not completely inactive in photosynthesis. The amount assimilated was, however, small in comparison with the leaves and varied with the different varieties and different conditions. In some instances, the total weight actually decreased, indicating that assimilation here could not balance the loss by respiration. The loss from the stems of the defoliated plants was always larger than that of the intact plants and was the larger the more the leaves were removed. The result showed that there are substances in the stem which are not normally used in seed development but are drawn upon when the formal supply becomes insufficient such as induced by defoliation. The amount drawn, however, could never make up the normal contribution from the leaves. Preliminary analyses were made on one variety to ascertain the nature of the substances drawn from the stem to the ear. It was found that from the time of flowering to full-ripe, about 1/2 of the proteinous material and all of the starch and soluble sugars disappeared from the stem in both intact and defoliated plants. Cellulosic material was usually only slightly used but when the plants were defoliated, the cellulosic materials of the lower internodes decreased greatly. Apparently these substances are not normally called upon for seed development but are drawn when the supply is inadequate. It also explains the weakness of the lower internodes and the tendency to lodge. Removing the lower leaves and the keeping the flag leaf intact resulted in a slight decrease in the final total weight, whereas the removal of the flag leaf alone produced no observable effect. The loss in the final total weight resulted from complete defoliation was larger than the sum of the losses resulting from the separate removals of the upper and of the lower leaves. This finding indicated that there exists a compensatory mechanism between the leaves so that the removal of one leaf will enhance the assimilatory activity of the remaining ones. This interesting phenomenon is being further investigated. Another effect of defoliation was the decrease in the percentage of “full grains”. Removal of part of the spikelets of the ear resulted in a higher percentage of “full grains”. Apprently one of the causes of empty and partially filled grains was the insufficient material supply from the leaves. The results were discussed in connection with the compensation of assimilatory activities among the leaves, the dominance of the ear over the material supply of the plant, and the location, time course and nature of the material transported from stem in relation to ear development and lodging.