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 :— i 
1. Nutrition (7.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, 7.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. 
