CHROMOSOMAL ABERRA TIONS 



197 



of three classes: (1) standard plants with normal chromosomes in dupli- 

 cate, (2) structural hj^brids, and (3) modified plants with the translocated 



Fig. 144. —Synaptic complex forined in inicrosporocyte of maize plant heterozytious for a 

 reciprocal translocation. {After B. McCIintock.) 



Fig. 115. — First meiotic division in microsporocytes of a .strain of wheat {Triticum) 

 heterozygous for a reciprocal translocation. 1, cross configuration in prophase. 2, ring- 

 of-4 at diakinesis. 3, metaphase; members of ring about to disjoin alternately. 4, 5, 

 adjacent disjunction; metaplia.se and early anapliasc. G, anaphase. (After L. Smith.) 



chromosomes in duplicate. These three types tend to occur in the ratio 

 of 1:2:1. 



Among plants, both types of homozygote, standard and modified, 

 commonly show a regular formation and disjunction of bivalent chromo- 



