232 PLANT LIFE 



In this particular nuclear division we find 

 that the chromosomes are not longitudinally 

 divided and the moieties then distributed be- 

 tween the two daughter nuclei, but that the 

 whole process is carried through in another 

 way. 



The earliest stages resemble those of an 

 ordinary vegetative nucleus which is about 

 to divide. The chromatin-containing gela- 

 tinous strands make their appearance, and the 

 chromatin is arranged in parallel streaks. 

 But instead of going on to differentiate and 

 finally to divide, the chromosomes proceed 

 to unite in pairs. We have very strong 

 grounds for believing that in no case is this 

 union a chance one, but that a chromosome 

 descended from one contributed by the sperm 

 unites with another corresponding to it but 

 derived from the egg. In other words, each 

 pair consists of a chromosome of maternal 

 and a paternal origin. 



The net result, then, of the approximation 

 and union of the paternally and maternally 

 derived chromosomes to form the respective 

 pairs is, of course, a reduction to one-half of 

 the number apparently present. 



Each pair now behaves as if it were a single 

 chromosome. They flock to the equator of 

 the spindle, but when they divide there, what 

 happens is simply a disjunction of the two 

 members of each pair, one of the members re- 

 treates to one pole, the other one to the other 

 pole. Hence a real reduction is now effected, 



