32 LABORATORY METHODS OF 



stain will take reddish-brown ; then the acid will attack 

 the cellulose and convert it into dextrine; then the 

 whole will be reddish-brown. At first all the starch will 

 be blue, due to the presence of the iodine solution. 

 Look for Brownian movement; this is an independent 

 movement which is not due to vitality. 



Exercise No. 19. Make a section of a potato and 

 search for starch granules. 



1. Place the potato in the microtome and cut sec- 

 tions 20 microns thick. 



2. Place a section on the slide and search 'for a 



field in which to make observations. 



3. Note the morphology of the cells and the con- 

 tents of the same. 



4. Place a cover on the section and irrigate with 

 iodine solution. 



5. Make notes. 



This is the mode of making a micro-chemical ex- 

 amination. Note that the morphology in this case is 

 not the same as in the onion cell, 



