1 8 FUNGOID DISEASES 



culture or farmer should be without one — but for a 

 more critical examination a microscope is necessary. 

 Spread of Disease. — The spread of disease may 

 be brought about in a variety of ways, the chief of 

 which are enumerated below : — 



1. Movement of disease spores in the atmosphere 

 by wind. 



2. Spores or diseased parts of plant carried by 

 animals, man, implements, etc. 



3. Transportation of infected soil by animals, 

 implements, etc. 



4. Growth of fungus from centre of infection. 

 The spores which constitute the chief form of 



reproduction in parasitic fungi are exceedingly 

 minute, and when detached from the fungus threads 

 most of them are easily carried by the wind from 

 place to place, thus spreading the disease. This is 

 well instanced in the spores of the fungus causing 

 potato disease {^Phytophthord) which are carried from 

 field to field ; and accounts for the rapidity of its in- 

 crease, and extent of its devastation, under favour- 

 able conditions (see later). These same spores, and 

 those of other fungi not carried by wind, may be- 

 come attached to the feet or bodies of insects, birds, 

 rabbits, man, implements, etc., and thus disseminate 

 the disease. Diseased plants when carted from the 

 root shed and thrown on previously uninfected 

 areas cause direct contamination, as also does the 

 manure from cattle which have eaten diseased 



