The Potatoe Plague. 97 



act of fermentation or putrefaction, has lately given rise to 

 the opinion that these actions themselves, and. the changes 

 suffered by the bodies subjected to them, are produced in 

 consequence of the developement of fungi, or of microscopical 

 animals, the germs, or eggs of which are supposed to be dif- 

 fused every where, in a manner inappreciable to our senses ; 

 they are supposed to be developed when they meet with a 

 medium fitted to give them nourishment. 



" It is ..certain that sponges and fungi, growing in places 

 from which light is excluded, follow laws of nutrition differ- 

 ent from those governing green plants ; and it cannot be 

 doubted that their nourishment is derived from putrefying 

 bodies, or from the products of their putrefaction, which pass, 

 directly into this kind of plants, and obtain an organized 

 form by the vital powers residing within them. During their 

 growth they constantly emit carbonic acid, increasing in 

 weight at the same time, while all other plants, under similar 

 circumstances, would decrease in weight. Hence it is possi- 

 ble, and indeed probable, that fungi may have the power of 

 growing in fermenting and putrefying substances, in as far as 

 the products arising from the putrefaction are adapted for 

 their nourishment." 



The truth with regard to the appearance of fungi in pota- 

 toes is, then, simply this : The disease exists in the potatoe ; 

 putrefaction takes place, and these germs or eggs which Xiebig 

 supposes to be every where, find in the diseased potatoe their 

 proper nourishment, and hence they begin to grow. If, as 

 is asserted, the germs of fungus are diffused every where, 

 why do they not affect all other crops, in a similar manner ? 

 Simply because other crops are not diseased. But over-ripe 

 vegetables, fruit, and decaying or putrefying vegetable sub- 

 stances are affected in a similar degree, because they are 

 putrefying: they are not putrefying because of the fungus. 



But, admitting for a moment that the presence of fungi is 

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