12 THE FLOWERING PLANT. 



movements and their modifications are only one result of spon- 

 taneity and irritability. 



Multicellular plants carry on precisely the same functions as 

 unicellular ones, namely : — 



t. Nutrition (i.e., Reception and Assimilation of food). 



2. Katabolism (including Respiration). 



3. Reproduction. 



4. Motility. 



5. Irritability and Spontaneity. 



Here, however, different cells undertake different functions, 

 and are specially modified for the performance of those functions. 

 In other words, physiological division of labour is accompanied 

 by morphological differentiation. This principle is most strik- 

 ingly exemplified in the highest, i.e., the flowering, plants ; but all 

 gradations of complexity are found in the vegetable kingdom, 

 from the simple cell upwards. 



In the following chapters, Root, Stem, and Leaf will be treated 

 of ; and as Hair- structures may occur on any or all of these, they 

 will not be dealt with in a separate chapter, but be mentioned 

 where necessary. 



