72 THE PLANT: A GENERAL INTERNAL VIEW 



23. Cells and Protoplasm. — Suppose we were to take 

 the stem of some common weed, cut a very thin cross 

 slice of it with a razor, and then examine it under a micro- 

 scope. It would look a good deal like Figure 24. We 

 would see a great number of very small compartments of 

 different shapes and sizes. These little compartments and 

 what they contain are called cells. 



But this discovery that plants are composed of cells is 



only the first step 

 toward learning 

 about the life 

 which goes on in- 

 side of these cells. 

 What you see in 

 Figure 24 might 

 be called the 

 framework or 

 skeleton of plant 

 life. This frame- 

 work is not it- 

 self alive. That 

 which is alive is 

 a colorless, trans- 

 parent substance 

 inside the cells. 

 This living substance is called protoplasm. You will find 

 protoplasm to be an exceedingly important word in this or 

 in any other study of living things. 



Huxley called protoplasm the physical basis of life. No 

 better definition has been given to it. Just what it is no 

 one knows. The most striking thing about it appears to 

 be that it is constantly changing. But, as long as it is 





His* 



Fig. 24. — ■ Cross section of the stem of the castor-oil 

 plant. This is not a woody plant. It dies in winter. 



