CHAPTER IX 



DISEASES CAUSED BY FUNGI 



Both animals and plants suffer from the attacks of fungi, and some 

 fungi are also attacked by other kinds of their own class. The 

 higher plants suffer most, and it is certain that every flowering 

 plant has one or more kinds of fungi that look upon it as their 

 legitimate prey. Even the seaweeds do not escape. Many^of the 

 most destructive fungus parasites are of microscopic dimensions, 

 as tlie numerous rusts and smuts so destructive to cereals and other 

 plants, and the majority of the blotches and spots on leaves and 

 fruit are caused by parasitic fungi. On the other hand, the large 

 bracket-shaped or hoof -shaped woody fungi growing on the trunks 

 of living trees are injurious parasites. 



It has been estimated that the annual loss on cultivated plants 

 throughout the world, due to the ravages of fungi, amounts to at 

 least £2,000,000,000. As examples of specific cases, the coffee-leaf 

 disease in Ceylon caused a total loss amounting to ^^17, 000,000. 

 An estimate by the Prussian Statistics Bureau gives the loss on 

 cereals in that country from rust alone, in one year, as ;{20,ooo,ooo. 

 In the United States the annual loss on apples from bitter-rot is 

 estimated at ;ir2, 500,000. Numerous other examples could be 

 furnished. In this country no official estimate of the annual loss 

 caused by fungi is made, but it is perfectly certain that such loss 

 amounts to an enormous sum. 



The above accounts refer to diseases which, owing to exceptional 

 climatic or other conditions, enable the disease to become of the 

 nature of an epidemic, but even in those years when epidemics 

 are absent, fungi are in\'ariably at work, and causing more or less 

 loss. 



It is an established fact that parasitism in fungi is an acquired 

 habit. Some of the reasons for this statement are as follows : 

 Throughout the fungi every grade of parasitism may be observed, 

 from the incipient stage where the fungus, as it may be stated, 

 lacking experience, kills its host-plant within a very short period of 

 time, thus limiting its own period of existence to a matter of days, 

 or in some instances, even of hours. To this category belongs the 

 minute fungus {Pytkium) causing " damping-off " in seed-beds, where 

 the tiny seedlings are attacked, fall over, and die within a few hours. 



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