DISEASES OF ECONOMIC 

 PLANTS 



INTRODUCTORY 



Subdivisions of Plant Pathology 



Plant Diseases may be considered under five heads : — 



1. Those caused by cryptogamic parasites, fungi, bac- 

 teria, and slime molds. 



2. Those caused by parasitic flowering plants. 



3. Those caused by animal parasites, insects, worms, etc. 



4. Those due to adverse inanimate environmental con- 

 ditions, light, water, soil, nutriment, etc. 



5. Physiological diseases due to other internal derange- 

 ment. 



Under the last head are grouped many diseases which 

 undoubtedly will fall under one of the other groups when 

 our knowledge concerning them is more nearly perfect. 



Owing to the entirely different nature of the causes of 

 the diseases classed under these groups, their study falls 

 to the lot of separate specialists : the first group to the 

 mycologist and bacteriologist ; the second to the botanist ; 

 the third to the entomologist and zoologist ; the fourth to 

 a large extent comes within the scope of the 'agronomist, 

 and the last is in the domain of the physiological botanist. 

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