Division in the Root of llcia Faba. 177 



to be due to the chromatin. When the thread first forms, it 

 is of a bluish crimson tint and is formed from the nuclear sub- 

 stance. This nuclear substance contains but a very small 

 quantity of chromatin, so that while the nuclear thread con- 

 tains some chromatin derived from the nuclear material, the 

 quantity thus obtained must be relatively small. The chro- 

 matin which eventually fills the thread and gives it its dense 

 bluish black color is mainly nucleolar material. We have 

 here merely a temporary change in form. The nucleolus is 

 chromatin material, and the chromosomes are chromatin 

 material. In the resting stage we find the chromatin chiefly 

 massed together in this large bluish black nucleolus ; in 

 the dividing nucleus, the nucleolus is transferred from its 

 acfsresrated condition and is distributed along the nuclear 

 thread. Therefore, as the reserve chromatin mass, i. e., the 

 nucleolar substance is passing out into the nuclear thread, 

 the nucleolus itself gradually disappears. 



We can now proceed from the stage where the spirem has 

 split transversely into the chromosomes. The nuclear mem- 

 brane has already disappeared, it having started to disappear 

 as the nucleolus passes its substance to the spirem. The 

 chromosomes split longitudinally, and thus are formed the 

 daughter chromosomes (Fig, 15). There are in most cases 

 five daughter chromosomes. Four is not an unusual num- 

 ber to find, but five seems to be the more common. The 

 daughter chromosomes now pass to opposite ends of the cen- 

 tral spindle. They collect at the ends of the spindle and for 

 a time retain their individuality (Fig. 16). Soon the individual 

 chromosomes can no longer be distinguished, since they 

 aggregate to form a small dense blue-black coil (Figs. 16 and 



17). 



Reappearance of the Nucleolus. — The chromosome coil 



now begins to heap up its chromatin material and we have the 



beginning of the formation of the nucleolus. The very earliest 



12 



