STERILE POLYPLOIDS 



219 



chromosome number. This variability arises in two ways. In 

 sexually reproducing species the irregular segregation of the multi- 

 valents gives gametes with various numbers ; owing to the high 

 gametic number the unbalance of these is less serious than it would 

 be in low polyploids, and they are not eliminated (v. Ch. VIII). 



tfO 



50 



T\Ochna SerruUfa. (Ciimrug, tmJ fptneim) 455 cAra. 



I \ 



I \ 



I V 



/ \ 



/ \ 



/ /\Tu/lpa c/us/ana (/\/eu>fo,i 3„J lLr/,nffwt) 300 chrs 



Types of Co/ifi^uraNons. 



Fig. 75. — Graph showing the percentages of different types of 

 configuration in two autopentaploid species at meiosis in the 

 pollen mother-cells. The more frequent high configurations in 

 Tidipa Clusiana are probably due to a higher chiasma frequency ; 

 cf. Yamamoto, 1935, on autohexaploid Rumex. 



In the polyploid species of Agave, on the other hand, the smaller 

 chromosomes are frequently distributed unevenly at mitosis, and 

 owing to their presence being indifferent in a high polyploid they 

 are often lost. The result is that the tetraploid and pentaploid 

 species have the full complement of five long chromosomes regularly 

 multiplied, while the short chromosomes are lacking to a variable 

 extent. 



