CAUSES OF RUST IN WHEAT. 183 



opinion that the disease is taken up by the root, every ex- 

 periment to communicate it from infected straw to others 

 proving abortive, and, indeed, if it were introduced into the 

 ear of the plant, how could it descend, and infect solely the 

 stem, which is the case, unless when the disease is in- 

 veterate ]" 



As to the fungus passing into plants by the roots, or being 

 prevented from propagating by any of the means here 

 pointed out, it appears almost too preposterous to be 

 seriously thought of. 



How difficult do our housewives find it to exclude the 

 seeds or prevent the fungus growing on their pickles and 

 preserves, even by tied down bladders and tight corks'? 

 And if horse dung in a mass be placed in certain situations, 

 it is well known that even the large edible mushrooms 

 will rise and grow where they never were seen before. 



Thus, then, if the cause of the rust or black blight be 

 as I have stated, and the observations both of Sir John 

 Sinclair and Mr. Knight confirm my opinions, and the ob- 

 servations of Sir Joseph Banks do not controvert them 

 the remedy is simple and obvious; viz., for the production 

 of seed crops, let manuring follow and not immediately 

 precede them ; or, at any rate, dung should not be ploughed 

 in on such lands, immediately before sowing the seeds. 



And it is equally obvious that the ploughing in green 

 crops must be conducive to the production of rust. And the 

 feeding off turnips with sheep, or folding them on the land, 

 immediately before sowing, must have a strong tendency 

 to the same effect. 



If, when lands are manured, two or three succulent or 

 green crops be taken off before it is sown for seed crops, 

 although the leaf and plant, or straw or haulm of such 

 crops may not appear so luxuriant in consequence, the seed 

 will be larger in quantity, and finer in quality. And if, in 

 the general course of cultivation, dung be applied or given 

 to the green crops, the luxuriance of leaf, stalk, &c., will 

 be produced in that form which is most valuable, either as 

 green food, turnips, &c., or hay; and the succeeding grain 



