66 EXPERIMENTS WITH PLANTS 



ance of the cells under the microscope. Each cell 

 has a cell -wall (cw) composed of cellulose, a firm 

 substance almost identical in nature with ordinary 

 paper or cotton or linen cloth. Within this firm cell- 

 wall is the living substance or protoplasm ( pr ) , soft 

 and jelly-like in consistency, which can be made 

 clearly visible if we place the sections in weak eosin 

 solution. It takes up the eosin rapidly and becomes 

 deep red in color, leaving unstained the cell-wall and 

 the starch - grains (st), which are the white glistening 

 bodies embedded in the protoplasm. If we place 

 some sections in iodine (see page 164) the starch-grains 

 become bluish black and the protoplasm yellow. If 

 we place other sections in safranin solution until they 

 are deeply stained and then rinse in alcohol until they 

 fade 10 a deep pink, we shall find in each cell a small, 

 deeply stained body called the nucleus (ri) ; this can 

 be more easily seen in the outermost row of cells 

 (where there are no starch-grains to obscure it) , and 

 still more easily in sections of the caulicle. Every 

 living cell contains protoplasm and a nucleus, and is 

 usually -surrounded by a cell- wall. 



The living substance (protoplasm) of the cells is 

 the source of all their activities. It may be killed in 

 a variety of ways; e. g., by heat, poisons, etc. It 

 then behaves very differently to what it does when 

 alive. We may kill some seeds to see how this affects 

 their power of growth. The most convenient way to 



