HYBRIDIZATION IN THE EVOLUTION OF MAIZE 



189 



effect. Figures 11.3, 11.4, and 11.5 show ears of corn heterozygous for blocks 

 of genes from chromosomes 3 and 4 respectively, compared to "pure" corn 

 in the same progeny. The blocks of genes from corn are much more "potent" 

 (a term proposed by Wigan, 1944, to describe the integrated dominance 

 effects of all genes) than the block of genes from teosinte, at least in the 

 striking characteristics which differentiate the two species. This is in itself a 

 noteworthy phenomenon since corn is not strongly "dominant" or more po- 

 tent than teosinte in the Fi hybrid, where both species contribute more or 

 less equally. 



Fig. 11.4 — These ears are the exact counterparts"]<)f those in Figure 11.3 exce])t that the 

 block of teosinte genes was derived from chromosome 4 of Florida teosinte. 



