180 CULTURE OF FARM CROPS. 



the same year. These circumstances tend to prove that 

 the rust does not depend solely on atmospheric influence, 

 otherwise it could not be prevented by changes of seed or 

 by the crossing of different varieties." 



This theory of Mr. Knight's is, like many others of his, 

 grounded on a superficial view of things, and is a mere 

 fallacious hypothesis. 



Indeed all these great naturalists appear to have be- 

 wildered themselves in specious theory ; and from not hav- 

 ing traced the operations of nature to its source, have 

 throughout mistaken the effect for the cause. 



Suppose a farmer was to find a sheep, unhappily reduced 

 and preyed upon by maggots or the larva of the flesh fly, 

 he may very justly suppose that the maggots reduced the 

 sheep ; and as justly expect, that whatever sheep were sub- 

 jected to the maggots would be reduced in the same man- 

 ner. Then what would be the best and proper remedy ? 

 Knowing the maggots to be produced from eggs deposited 

 by flies, would he try to cover his sheep from the flies ; or 

 attempt to drive them where there were no flies ? Where 

 is the farmer or shepherd that does not know that flesh 

 flies will not deposit their eggs on a healthy part of a sheep ; 

 or if they do, that they will not produce maggots ? They 

 know full well, that if a sheep be diseased by eruptions or 

 wounded, the flies will find out these places, and there de- 

 posit their eggs ; and, therefore, the remedy is simple. 

 Cure and prevent the disease, or protect the wounds, and 

 the evil is avoided. " Eemove the cause, and the effect 

 ceases." 



Very similar will be found the diseases in wheat, called 

 the rust or black blight, and its cause. 



The fungus undoubtedly preys upon that which is in- 

 tended to nourish and sustain the wheat ; but what afforded 

 an attraction and lodgment for the fungus ? This is the 

 grand question. 



It is stated, that the fungus is a parasitical plant, like 

 the misletoe, but this is not the fact ; the fungus has no 

 power to attach itself to, or penetrate, the healthy stalks of 



