II 



PRACTICAL EXERCISES ON THE STRUCTURE OF THE VEGETABLE 

 CELL INVOLVING SIMPLE METHODS OF PREPARATION. 



Before entering upon the work described below, the preceding 

 pages should be carefully read through, otherwise the beginner 

 will be apt to make serious mistakes in manipulation. 



NOTE. The method of mounting fresh material in water 

 will be used throughout this chapter : it has the following 

 advantages : 



1. It is the simplest possible. 



2. The cells are seen unaltered, i.e. in the living state, and 

 it is thus specially suitable for observations on fresh material. 



3. When thus mounted the effect upon the living cell of any 

 reagent soluble in water may be observed by irrigation : thus 

 it is the natural starting-point for the study of the micro- 

 chemical reactions of the living cell. 



It is however open to objection on the following grounds : 



1. The slides thus prepared cannot be kept, since the water 

 would evaporate. 



2. The refractive index of water being relatively low, the 

 objects do not appear so transparent as in more highly 

 refractive media. 



3. Bubbles of air are very apt to be included with the object. 



I. The first object to be examined will be the filamentous 

 Alga, Spirogyra. 



