Phosphatase activity in the dormant bean seed is low. The embryo contains a much higher concn. of the enzyme than the cotyledons. The enzyme concn. is much greater in the germinated than in the dormant seed. The very low concn. of phosphatase in the cotyledons during the early stages of germination is not due to the presence of inactivators. In the leaves, after they have emerged from between the cotyledons, the phosphatase activity gradually rises and reaches a max. after a few days. The concn. of enzyme in the leaves at its optimum is higher than that of any other part of the plant throughout its entire life history. In the flowers the enzyme concn. is low and is comparable with that found in the leaves of a fully matured plant. The phosphatase content of the pods is equal to that of the flowers. The newly forming beans have a very low enzyme concn. In the potato plant which is sprouting from the tuber the greatest enzyme concn. is found in the leaves, and much smaller concns. are found in the stem; in the tuber and roots only slight traces can be detected by the methods employed. In the radish, phosphatase is present in all parts of the plant, the greatest concn. being found in the leaves. In the wheat grain the enzyme increases in concn. during germination. The greatest phosphatase content, however, is found in the plumules. The concn. of the enzyme in the rootlets was intermediate between that of the grain and the plumule.