164 



MAIZE 



CHAP, reference to the most striking or important characters, and speak 

 v - of a plant as being homozygous for this or for that character. 



127. The Heterozygote. — The 

 heterozygote is formed by the 

 union of gametes bearing the two 

 characters of an allelomorphic pair 

 (if 129). It is the progeny of 

 parents which are dissimilar in 

 some, or all, characters, and may 

 be either exactly like one parent, 

 or may have derived some visible 

 characters from each parent, in 

 which case it will not be exactly 

 like either, i.e. in all its main 

 characters. 



The progeny of a heterozygote 

 are unlike; some are more or less 

 like one, and some like the other 

 parent, while some are unlike either. 



128. Unit-Characters. — We 

 learned from the preceding chapter 

 that in maize the two gametes or 

 sexual cells, which unite to form 

 a zygote, often come from separate 

 plants. These two plants may 

 belong to different breeds, having 

 different characters. We know 

 from experience that if a white 

 dent breed is fertilized with pollen 

 from an ordinary pure-bred yellow 

 dent breed, the resulting grain 

 (i.e. of the first generation) will be 

 yellow dent, but that in the fol- 

 lowing generation some grains on 

 one and the same ear will be white 

 and some yellow ; or that if we 

 cross a sugar breed, havingwrinkled 



Fig. 71. — A heterozygous 

 ear of the F 2 seed generation of 

 a cross between black wrinkled 

 and white dent (IT 127). 



grain, with pollen of a flint breed having rounded grain, the 

 resulting grain will be round and flinty. That this is due not 

 merely to what has sometimes been called " prepotency of the 



