CHAPTER II 



CAUSES OF ILL-HEALTH IN PLANTS 



JxjST as a plant is in perfect health when all its organs 

 are perfectly attuned to its surroundings, and no one 

 function outpacing the others upon which it partly 

 depends, but aU concerting in harmony for the 

 common good, so when anything occurs beyond the 

 power of the plant to adjust itself to and discord 

 arises, ill-health will supervene and the whole suffer. 

 The discord may be due to changes in the plant 

 itself, possibly perfectly natural and occurring in 

 the due sequence of its development, or it may be 

 due to changes in the environment. In the latter 

 we have to incljide not only the soil, water, atmo- 

 sphere, temperature, and light, but also its living 

 neighbours, and especially such as are likely to prey 

 upon it among animals and fungi. 



The changes which occur naturally in the plant 



^self are generally looked for, and are less deplored 



than those which bring about disease through acting 



from without. A good example is provided by those 



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