CELL MULTIPLICATION 



125 



the distribution of the chromosomes. At this stage it becomes 

 apparent that each chromosome consists of two pieces or halves, 

 each apparently having spUt longitudinaUy. The halves of each 

 chromosome now separate, pass to opposite ends of the ceU where 

 the new nuclei are formed. Thus each new nucleus gets as many 

 halves, which soon grow to full size chromosomes, as there were 

 chromosomes in the parent cell. As the new nuclei are forming 



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Fig. 110. — Cell division, a, cell in resting stage. 6, chromatin formed 

 into a thread, c, the thread of chromatin broken into segments called chromo- 

 somes, d, chromosomes arranged across the cell for division. Notice the 

 threads called spiadle fibers running through the cell and that the nuclear 

 membrane has disappeared, e, chromosomes have spht and the halves are 

 passing to opposite ends of the cell. /, chromosomes have reached the points 

 where they are to form new nuclei, g and h, new nuclei and cross wall be- 

 tween them forming. 



a cross wall is formed, which divides the cytoplasm, and cell divi- 

 sion is now complete. Instead of one cell there are now two, 

 each of which after growing to full size will divide in the same 

 manner as the parent cell. 



Except in certain regions where cell multiplication is the spe- 

 cial function, most cells of the plant sooner or later lose their 

 ability to grow and divide as a result of their modifications 

 which adapt them to their special functions. Thus after cells are 



