188 



PAUL C. MANGELSDORF 



brid, vegetatively luxuriant, potentially capable of producing great numbers 

 of seed. Measured solely by total grain yield, the Fi hybrid does not exhibit 

 heterosis since its grain yield is considerably less than that of corn, but meas- 

 ured in terms of number of seeds, or number of stalks, or total fodder, the 

 hybrid certainly exhibits heterosis. 



In the modified inbred in which a block of genes from teosinte has been 

 substituted for a block of genes from maize, the situation is quite different. 

 There are no functional aberrations so long as the block of genes from teosinte 

 is heterozygous. Under these circumstances it has very little discernible 



Fig. 11.3 — Ears of a teosinte-modified inbred strain 4R-3 which are isogenic except for an 



introduced block of genes from chromosome 3 of Florida teosinte. The ear at the left lacks 



the block of teosinte genes, the center ear is heterozygous for it, the ear at the right is 



homozj'gous for it. Note the high degree of dominance or potence of the maize genes. 



