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, insects, 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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