The high-lysine gene in Riser mutant 1508 conditions an increased lysine content in the endosperm via a changed protein composition, a decreased seed size, and several other characters of the seed. The designation lys3a. !vs36, and lys3c, is proposed for the.allelic high-lysine genes in three Riser mutants, nos 1508.18, and 19. Linkage studies with translocations locate the Lys3 locus in the centromere region ofchromosome 7. A linkage study involving the loci lys3 and ddt (resistance to DDT) together with the marker locifi (fragile stem), s(short rachilla hairs), and r (smooth awn) show that the order of the five loci on chromosome 7 from the long to the short chromosome arm is Y, s,fi, lys3, ddt. The distance from locus I to locus ddt is about 100 centimorgans.