PROTOPLASM AND NUCLEUS 43 



sote (see Appendix A), in which they should be left for 

 some minutes, so that the fluid may thoroughly per- 

 meate them : then mount in Canada balsam dissolved 

 in benzol. 



Examine sections thus treated under a high power, 

 and observe the chief bulk of the tissue to consist of 

 square or oblong cells of considerable size : the following 

 parts are to be recognized : 



1. The cell-wall, which is uniformly thin and is 

 stained. 



2. The protoplasmic lining or primordial utricle, 

 which is also stained. 



3. A large central vacuole, which is not stained, and 

 is usually traversed by fine bridles of slightly stained 

 granular protoplasm : these suspend in a central 

 position 



4. The deeply stained nucleus : it may be observed 

 in many cases that the nucleus does not occupy a 

 central position, but is embedded in the peripheral 

 protoplasm, while the whole cell-cavity is occupied by 

 a large vacuole. 



Examining the nucleus more closely there may be 

 distinguished 



a. Deeply stained nbrillse, forming apparently a 

 convoluted coil, or a reticulum : this is the chromatin. 



1}. An unstained matrix in which the nbrillse are 

 embedded the achromatin. 



Pith of a very young shoot of the Elder will also 

 serve as good material for these observations ; the 

 young shoot should be treated as above directed, and 

 longitudinal sections will afford similar results. As an 

 alternative method of preparation, which has the 



