4 



ANAPHASE I DYADS 



A 



11 



7 8 



METAPHASE H DYADS 



J ii I ^ 



12 13 »U ^15 



10 



i 



12 



ANAPHASE IE MONADS 



t 



16 



Fig. 4.5 — All figures are from carmine smears of homozygous abnormal 10 plants. Figures 

 1-5 represent various configurations found at anaphase I. Figure 1 is a normal dyad with 

 chromosomal fibers formed only at the true centric region. In Figure 2, two arms have 

 formed neo-centric regions. The true centric regions appear to be inactive. Figure 3 shows a 

 dyad with two neo-centric regions and an active true centric region whose chromosomal 

 fibers are directed away from the nearest pole. Figure 4 is a dyad with a single neo-centric 

 region. In Figure 5 the two neo-centric regions are directed to opposite poles. Figures 6-7 

 illustrate various metaphase II dyads. The location of the equatorial plate is represented 

 by horizontal lines. Figure 6 is essentially normal with no formation of neo-centromeres. 

 Figure 7 is a dyad with two neo-centric regions directed toward opposite poles. There is a 

 single neo-centric region in Figure 8. Figure 9 is a dyad which is disjjlaced from the equa- 

 torial plate. The true centric region has divided to form two independent monads. Each 

 monad has formed two neo-centric regions which are oriented toward opposite poles. In 

 Figure 10 one of the monads has its two neo-centromeres directed to opposite poles. Fig- 

 ures 11-16 are illustrations of monads found at anaphase II. Figure 11 is a normally dis- 

 joining monad. In Figure 12 a single neo-centromere is evident. Figure 13 shows two neo- 

 centric regions. Figure 14 has a single neo-centromere which was active at metaphase II. 

 In Figure 15, chromosomal fibers have arisen from two neo-centric regions and also from 

 the true centric region. The true centric region and the neo-centromeres are acting in op- 

 posite directions. Figure 16 shows a monad with two neo-centric regions which are directed 

 toward opposite poles. This type of monad is derived from those shown in Figure 9. 



