This group, which is concerned with the applications of mathematics to agricultural science, is sponsored by the Biotechnology and Biological Sciences Research Council. It was formed in 1970, and has since met at approximately yearly intervals in London for one-day meetings. The twenty-fifth meeting of the group, chaired by Dr T. M. Addiscott of the Institute of Arable Crops Research, Rothamsted Experimental Station, was held in the Wellcome Meeting Room at the Royal Society, 6 Carlton House Terrace, London on Friday, 15 April 1994, when the following papers were read.