Thomas Johann ("Tom") Arnason was born in Brown, Manitoba, in 1905. During his long career at the University of Saskatchewan he taught in a broad range of specialties in plant biology, including morphology, evolution, cytology and genetics. His research activity included studies on gene transfer in wheat hybrids, meiotic behaviour of corn-teosinte hybrids, sterility in potatoes, maternal inheritance in the cereals and mutagenesis by ionizing radiation and alkylating agents. He and one of his students, ME. Cummings, were among the first to demonstrate chromosome anomalies induced by absorbed radioactive isotopes in plants. Professor Arnason was also active in the formation of the Genetics Society of Canada and served as its president in 1957-58. He was named Professor Emeritus when he retired from the University in 1972.