Colin Malcolm Donald has played an important part in initiating the research on which our present knowledge of pasture species and communities is based-studies of the species, their growth, variation, distribution, reactions to soil and climate; of the mineral nutrition of pastures, and of the nature and dynamics of fertility changes induced by pasture improvement. In recent years his thorough studies of the nature of competition in pasture communities have led him to an experimental and theoretical attack on the complex relationships between light intensity, leaf area and yield. In this field he has greatly enhanced his reputation as a plant scientist.