The F2 generation of the cross 'Williams' x 'Manchu (Madison)' was used to determine if the Ap and W1 loci were linked. The Ap locus controls a seed acid phosphatase which exists in the germplasm in three different electrophoretic forms controlled by three codominant alleles -- Ap^a, Ap^b and Ap^c (Hildebrand et al., 1980). The W1 locus controls flower color--purple (W1) and white (w1).