WHITE PLAINS, Aug. 10— Florence M. Crowther, a literary agent and the widow of Bosley Crowther, former motion-picture critic of The New York Times, died of cancer Thursday at the White Plains Hospital Medical Center. She was 75 years old and lived in Somers, N.Y.
Mrs. Crowther was a former associate of the New York City literary agent Blanche Gaines.
Before that she reviewed books on a freelance basis for The Times, for which also she did public relations in the early 1930's. She had also worked for CBS Inc. and NBC. During World War II she served in the Office of War Information.
Mr. Crowther died in 1981. Mrs. Crowther is survived by three sons, F. Bosley 3d, of Troy, Va., John M., of Los Angeles and Jefferson H., of Upper Nyack, N.Y.; a brother, Harold M. Marks of New York City, and five grandchildren.