Dr. Evans is distinguished for his work on the physiology of flowering. He has investigated the photoperiodic processes in the leaf to show what underlies the highly sensitive responses to day length in long and short day plants. He has developed the idea that flower stimulus might be a steroid and that the inhibitor might be abscisin. He has also investigated the role of the pigment phytochrome. Even more important are his studies of the events occurring at the shoot apex, which lead to differentiation of flowers. He has demonstrated transient increase in RNA synthesis and protein synthesis at the time of the stimulus has developed ingenious techniques to study shoot apices in vitro and has found two separate components of plant induction related to two separate photoperiodic processes. Dr. Evans has played a leading role in the development of the theory and practice of the Canberra phytotron, both in the pure and applied fields.