Miss Mary Gladys Sykes, British botanist, obtained a first class pass in both parts of the Natural Science Tripos at the University of Cambridge and was a research fellow of Newnham College when she married David Thoday* in June 1910. By that time she had published some 20 scientific papers under her maiden name, including 'The anatomy and morphology of Tmesipteris' [a genus of club mosses] (Annals of Botany, 1908), 'Notes on the nuclei of some unisexual plants' (Ibid, 1909), and 'The anatomy and morphology of the leaves and inflorescences of Welwitschia mirabilis' (Philosophical Transactions of the Royal Society of London, 1911).
From sometime before her marriage Miss Sykes collaborated with David Thoday in research on plant physiology. For example, they published 'Preliminary observations on the transpiration current in submerged water plants' in the Annals of Botany in 1909. In 1911 they moved to Manchester, where Mrs Thoday became an honorary research fellow in the University of Manchester. In March 1919 they arrived in South Africa for a stay of almost four years. During this period she published a paper on 'Ripening of seed in Gnetum gnenom and Gnetum africanum' in the South African Journal of Science (1920, Vol. 17, pp. 189-191).
The Thodays left South Africa for Bangor, Wales, where Mrs Thoday became an honorary lecturer in botany in the University College of North Wales. She was active in the women's suffrage movement, also during her stay in South Africa. All four her sons were on active duty during World War II (1939-1945), three of them in the Royal Air Force and one as a radio officer in the Merchant Navy. She died in 1943 after a long illness.