SUMMARYAcid phosphatase activity inClosterium acerosumhas been studied using the Gomori and the azo dye procedures. A modification of the Gomori method was used for detecting the distribution of acid nucleases. The plastid is the major site of acid phosphatase activity luhich may be primarily within pyrenoids, between pyrenoids, or throughout the plastid. The Gomori procedure showed activity within the pyrenoids or in the central core of the plastid, whereas the azo dye method showed activity throughout with an occasional tendency to be localized near the ends. No other cytoplasmic activity was ob‐served but evidence for occasional activity in the nucleus is presented. Alkaline phosphatase could not be detected. Acid nuclease activity, which results in the degradation of DNA, RNA, and RNA‐Core, has been found in both the nucleus and the plastid. Plastid activity is heat labile, whereas nuclear activity is only slightly diminished after 5 min at 100 C. The results arc interpreted as indicating at least 2 acid phosphatases and 2 nucleases inC. acerosum.The findings are discussed with respect to the distribution of similar enzymes in other organi