INTRODUCTORY 



of life which are among the most complicated and the 

 most perfect that nature shows us. 



So the life of a plant shows us conflict and struggle 

 waged against disadvantages of a very formidable 

 nature; a power of appreciating difficulties and of 

 struggling against them ; further, it exhibits a capacity 

 of seizing upon such advantages as present themselves, 

 not only in the air and in the soil, but in relative 

 association and competition with each other. 



We are familiar with the fact that part of an ordinary 

 green plant is embedded in the soil. Such a part is 

 commonly known to us as its 

 root, and we distinguish it in 

 several ways from the part 

 which rises into the air (Fig. i). 

 In the case of plants which live 

 in water we find much the same 

 division of the plant body. 

 There is in their case also a root 

 part, which is not green and 

 which is buried in the soil or 

 mud at the bottom of the 

 water ; there is a part which 

 stretches up into the water, in 

 some cases extending into the 

 air above the surface. We 

 often express this fact by say- 

 ing that the plant is differenti- 

 ated into a root and a shoot. 



This differentiation is a funda- FIG. i. Diagram showing the 

 mental one, for the two parts 

 behave very differently. They 

 always grow in opposite directions, and as these direc- 

 tions are generally upwards and downwards they are 

 spoken of as the ascending and the descending axes of 

 the plant. 



general structure of 

 dicotyledonous plant. 



