30 THE STORY OF PLANT LIFE 



Spines serve the double function of protection 

 against animals and drought. Hairs on leaves are 

 developed also as a protection against animals, as a 

 protection to the flower to prevent the honey being 

 stolen by creeping insects, and also to protect the 

 stomata from being clogged, and so causing a bar to 

 transpiration. Some hairs are glandular, and serve 

 to excrete poisonous materials, and act again as a 

 protection as in the Nettle. 



Reference has already been made to the adapta- 

 tions of leaves to shade or sun, and to an aquatic habit. 

 Herbaceous plants, with narrow, much dissected 

 leaves, are more exposed to air than other plants, 

 which may account for the prevalence of such leaves 

 or to the need for light, as they are often close in habit. 



The forms of leaves are again adapted to their 

 arrangement in the bud. The characteristics of the 

 remaining types of structure, the floral leaves and 

 fruits and seeds, have been described to some extent 

 in the Introductory Volume, and need not be 

 mentioned here. The main functions of the flower 

 are pollination and effective fertilisation, that of 

 fruits and seeds effective dispersal preparatory to 

 germination and race progression. 



14. The Structure of Plants, or Adaptations 

 TO Function. 



The structure of a plant, unlike that 01 its form, 

 cannot so well as the forms of plants be considered 

 in relation to the plant as a whole, but organ by 



