CHAPTER XIV 



THE DEFENSIVE EQUIPMENT OF PLANTS 



We have already, in the first part of this book, dealt with 

 the modifications found in plants which secure them 

 against the perils of unfavourable environment, and 

 especially lack of water. In the present chapter we are 

 concerned with the modifications which serve to defend 

 their possessors against the attacks of living enemies. 

 These enemies fall into two classes ; 



1. Those which feed on the tissues, producing disease — 

 e.g., bacteria and parasitic fungi. 



2. Those which feed on the tissues, injuring the plant 

 by the loss of the parts eaten, but not necessarily giving 

 rise to actual disease and injuring the plants vitally — 

 e.g., grubs, caterpillars, slugs, beetles, aphides, birds, and 

 browsing animals. The eel-worm, however, is a pest 

 which produces deadly disease in herbaceous plants, 

 especially when young. 



There is, as usual, no absolute distinction between the 

 two sources of injury. Any form of injury to essential 

 organs, especially those concerned with nutrition, may so 

 damage the individual as to set up a condition of feeble 

 health, which may result in disease and even in death. 



In surveying the weapons of defence — that is to say, 

 those modifications which serve to protect plants against 

 injury liable to be inflicted upon them by living organisms 

 — we shall consider separately — 



1. The fruit and the seed. 



2. The seedling. 



3. The adult plant. 



1. The Fruit and the Seed. — Here it is important that 

 while the fruit is eaten the seed should be preserved. 

 It is generally found that animals devour the fruit and 



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