174 Gardner — Studies on Groti'th and Cell 



Observations. 



The Resting Cells. — These are large and enclose a well- 

 formed nucleus. The nuclear substance, or nucleoplasm is 

 stained a bluish crimson. The nuclear substance of the cells 

 in the bean root contains but a very small quantity of chromatin. 

 By careful focusing it is possible to distinguish minute chro- 

 matin granules, stained somewhat darker than the very faint 

 linin threads. The nucleolus is a large, rounded mass, 

 and stains a dense bluish black. It may be in the centre of 

 the nucleus, or as is more usual, it is excentrically placed. 



Number of Nucleoli. — There may be one nucleolus present, 

 or more than one. The usual number in cells in the growing 

 apex is one, in cells back of the apex, it is as common a 

 feature to have two, as it is to have one. Very rarely are 

 three large nucleoli to be found. Frequently, in nuclei with 

 one or two large nucleoli, many small nucleolar fragments 

 are found. These smaller pieces are always recognizable as. 

 nucleolar material by their density and staining relations. 



Division. 



The first traces of division are to be seen in an aggrega- 

 tion of the nuclear material (Plate XVIII, Fig 6.). This 

 aggregation always occurs previous to the formation of 

 the spirem thread. The minute chromatin granules becom- 

 ing more massed together appear darker than in the resting 

 cell. The aggregation continues and the entire nuclear sub- 

 stance appears darker, due to massing together in small quan- 

 tities of its contents (Fig. 5). These small thread-like masses, 

 soon fuse into an almost continuous thin thread. During this 

 process the nucleolus retains its color relations, and as the 

 aggregation of the nuclear substance and the formation of 

 the thread occur, the nucleolus comes to lie in more and more 

 intimate relation with these. The nucleolus is related to the 

 nuclear reticulum in such a way that the fibers penetrate its. 



