HETEROPLOIDS 



173 



The frequency of occurrence of lata types varies in dif- 

 ferent progenies from 0.1 to 1.8 per cent, according to 

 Gates. 



At the maturation of the pollen of the 15 chromosome 

 types, 8 chromosomes are present. Seven are in pairs 



Fig. 100. 

 Oenothera lata. (After Anne Lutz.) 



and 1 is unpaired. The conjugants separate and pass to 

 opposite poles at the first maturation division. The un- 

 paired chromosome does not divide at this time, but 

 passes intact to one or to the other pole. Other irregu- 

 larities in the maturation divisions occur in some cases, 

 but whether or not they are caused by the extra chromo- 

 some is unknown, although Gates states that these irregu- 



