158 ON THE RUST OR 



" tinguished naturalist (Sir Jos. Banks), that tins 

 " disease is occasioned by the growth of minute 

 *' parasitical fungus, or mushrooms, on the leaves, 

 " stems, and glumes, or chaff, of the living 

 " plants ; and that the roots of the fungus, inter- 

 " cepting the sap intended by nature for the 

 " nutriment of the grain, render the grain lean 

 *' and shrivelled, and, in some cases, rob it com- 

 " pletely of its flour. Nor is that all ; the straw 

 *' becomes black and rotten, unfit for fodder, or 

 *' little better than a caput mortuum, possessing 

 *' neither strength or substance." 



Again, — " Several of the accidents, above 

 *« enumerated, may contribute to the production 

 *' of rust ; but there are two additional circum- 

 '* stances which likewise tend to promote it. 

 ** First, — Having the land in too rich a state for 

 " corn crops ; and. Secondly, — When too fre- 

 " quent a repetition of crops of wheat takes 

 " place." 



" It has been well observed, that when crops, 

 " intended to ripen their seed, are objects of 

 ** culture, there is not only wanted a degree of 

 *' vigour and luxuriance in the plants sufficient 

 *' for the purpose ; but if the fertility of the soil 

 *' be raised to a higher pitch than is necessary or 

 *' consistent with that object, injurious rather 

 " tlian beneficial consequences may be the result. 



