DEFENCES OF PLANTS 335 



success. It has defended itself against the aggressor, 

 and adapted itself to the demands of its habitat; the 

 weaklings that have attempted to resist its victorious 

 progress have been thrust aside and have perished by 

 the way, in most cases leaving not a trace of their former 

 existence. The plant which is to be successful must 

 hold its own ground and, if need be, extend it; it must 

 not allow itself to be suffocated by an aggressor, it 

 must have its place in the sun, and it must make the 

 best possible provision for the perpetuation of the 

 race. It has not only to compete with highly organized 

 species, but must defend itself against the incursions 

 of disease-engendering microbes and fungi. It must 

 be prepared for changes of temperature and other 

 climatic vicissitudes. In drought it must conserve 

 its water; at all times its protoplasts must be rendered 

 comfortable. Its mechanics must be so well ordered 

 that it may resist physical strains. It must be able 

 to stanch its wounds, lest they provide a vulnerable 

 point in its armour, at which microbes can attack 

 with success, or lest it bleed to death. It may be 

 attacked and eaten by animals if it does not render 

 itself objectionable to them. It may also be trampled 

 upon, but without mortal injury, if only it has suffi- 

 cient resources. Many plants, although gravely 

 wounded, are not beaten; they fall to rise again. 



In all its parts and in every stage of its develop- 

 ment, a plant is liable to attack from some quarter. 

 The seedling period is one of much delicacy. Fortu- 

 nately, the earth in which germination takes place 

 affords protection during the earlier developments, but 

 so soon as the tender plant emerges from the ground it 



