Chloroplasts lost their starch-synthesizing enzymes (phosphorylase, ADPGa-glucan glucosyltransferase) during a period of darkness. Enzyme activities returned in the light, but this process could be reversibly inhibited with actinomycin D or chloramphenicol. It is concluded that the enzymes are produced in the chloroplast and that starch production is dependent on the functioning of the protein synthesis as directed by the nucleic acids in the chloroplast. The localization and extension of DNA areas in chloroplasts and chloroamyloplasts showed a relationship to the number and size of the starch granules produced. In many cases there was a close contact between DNA areas and starch granules. DNA and RNA were found in a variety of plastids, in agreement with the expectation expressed by various authors. It is likely that all plastids contain their own mechanism for nucleic acid-controlled protein synthesis, and that the starch-synthesizing enzymes are always among the proteins thus produced.