MONOSOMATIC CELLS 



DISOMATIC CELLS 



TETRASOMATIC CELLS 



100 lM MO 230 300 350 400 450 500 550 600 630 700 750 870 830 600 050 1000 1050 1100 1130 l!00 1250 ~I300 



MICRONS FROM EXTREME TIPS OF ROOTS 



Fig. 19-14. Frequency distribution of mitoses with one, two, or four times the basic 

 number of chromosomes, in the root of Cucumis. Chromosome number increases with 

 distance from the apex ( left. ) ( From Ervin. ) 



' DAYS 



Fig. 19-15. Changes in nuclear volume (cubic 

 microns ) during development of maize endo- 

 sperm. C, central region. AB and AD, surface 

 layers. Nuclear growth here is due to endomi- 

 tosis, with increase in number and size of 

 strands per chromosome. Number of chromo- 

 somes presumably does not increase. ( From 

 Duncan and Ross. ) 



444 



Fig. 19-16. Endopolyploidy in tri- 

 chomes of Bryonia, a, glandular 

 hair with basal cell 256-ploid; 

 b, hair of filament, the basal cell 

 128-ploid, and others 16-ploid. The 

 epidermis is diploid. ( From Tscher- 

 mak-Woess and Hasitschka. ) 



