This group, which is concerned with the applications of mathematics to agricultural science, is sponsored by the Agricultural and Food Research Council. It was formed in 1970, and has since met at approximately yearly intervals in London for one-day meetings. The twenty-third meeting of the group, chaired by P. H. Nye of the Department of Plant Sciences at the University of Oxford, was held in the Wellcome Meeting Room at the Royal Society, 6 Carlton House Terrace, London on Friday, 7 May 1993, when the following papers were read.