Barber is distinguished for his contribution to plant cytogenetics. Contributed greatly to the knowledge of chromosome movement on the spindle by the study of time elapse photographs of living cells. Has advanced the knowledge of chromosome behaviour in many ways by experimental studies, including the origin of diplochromosomes following heat treatment, reaction of cold and colchicine on mitosis, and the discovery of multiple sex chromosomes in marsupials. Recently has turned to the study of the physiological genetics of flowering in Pisum. He has also studied the ecological adaptiveness of variation in Eucalyptus and of coat colour genes in wild rabbits in Tasmania.