Ill 



COMMON MICRO-CHEMICAL REACTIONS 



A FEW further practical exercises will now be given, 

 involving the use of common methods and reagents, and 

 leading to a fuller knowledge of the appearance and 

 reactions of the parts of the cell, and of some of the 

 bodies commonly contained in it. 



I. Cell-walls. 



A. Cellulose Walls. 



Take some ordinary unbleached " cotton wool," which 

 consists of unicellular hairs, from the surface of the 

 seed of the cotton plant (Chssypium), Moisten first 

 with alcohol, arid then soak in water. 



a. Mount a small quantity in water, and examine 

 first with a low, and then with a high power : observe 



1. The long, filamentous, unicellular hairs, which 



compose the " cotton- wool," coiled irregularly 

 together. 



2. The rather thick, highly-refractive and colour- 



less cell-wall. 



3. The remains of granular protoplasm, which 



may still be seen within. 



I), Soak a small quantity of the cotton for a few 



D 2 



