Division in the Root of Vicia Faba. \ 67 



the general literature on cell division, is that of Dr. T. Mont- 

 gomery, entitled, " Comparative Cytological Studies with 

 Especial Regard to the Morphology of the Nucleolus." His 

 observations are based upon animal cells and his conclusions, 

 briefly stated, are as follows : 



Number of Nucleoli. — The nucleoli vary in number from 

 one to five and in certain stages of some cells — there may be 

 several hundred. In a few cells no nucleoli are present. 



Positio7i of the Nucleolus in the Nucleus. — When a single 

 nucleolus is present it is always placed excentrically though 

 not against the nuclear membrane. Those cases where it 

 occupies the centre of the nucleus are to be regarded as 

 exceptional. In regard to this point the author says he is 

 unable to agree with Professor Macfarlane, who believes the 

 nucleolus to be the morphological and trophic center of the 

 cell. 



The nucleolus is often suspended in the chromatin network, 

 but not in such a way that the fibers penetrate its substance ; 

 they are merely wound around it. 



General MorpJiological Stj'ucture of the Nucleolus. — The 

 nucleolus may or may not have a membrane. Vacuoles are 

 normal structures in nucleoli since they may be seen after the 

 most diverse methods of fixation. To the nucleolini or 

 endonucleoli which Professor IMacfarlane regards as " the 

 tropic center of the cell and as an important mechanical agent 

 during nuclear division," the author attaches no morphological 

 significance. 



Amoeboid movements have been frequently observed in 

 nucleoli and these are in all probability normal, and perhaps 

 should be considered as an inherent function of the nucleolus, 

 since no movements in other parts of the nucleus are known 

 in a resting cell. 



Nucleolar division is of two kinds : (i) The mode by 

 which the nucleolus becomes elongated and then breaks into 



