Note: When Robert Emerson zvas killed in a plane accident on February 4. 1959, much of the experimental material accumulated in his two years work on the action spectrum of photosynthesis in the far-red region, remained unpublished. He zvas to present these results to the Botanical Congress in Montreal in August, 1959. Instead, the following paper was presented, prepared on the basis of Emerson's earlier talks and laboratory notes, and after consultation with his collaborators, R. V. Chalmers and C. Cederstrand. The theoretical discutssion of the results is my own. The presentation of this paper was intended as a memorial to Dr. Emerson; I was urged to publish it to give all those wvorking in the field access to the results of Emerson's last, exciting results. A paper presented by J. Myers (12) at the same mneeting provides both confirmation and interesting expansion of the phenomenon which is becoming knozwn as the Emerson effect*. In particular, it shows that the so-called chromatic transient, as observed after the replacement of illumination with light at 700 mu by illumination weith a shorter-wave light giving the same steady yield of photosynthesis, has the same action spectrum as the Emerson effect, i.e., suggests a specific role of chlorophyll b.-E. RABINOWITCH.