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XV. On the Mildew and some other Diseases incident to 

 Fruit Trees. In a Letter to the Secretary. By Mr. 

 John Robertson, F. H. S. 



Read November 20, 1821. 



Sir, 



I a m induced to trouble you with some observations, which 

 I have had an opportunity of making on the Diseases of Fruit 

 trees, in the hope that they may add somewhat to the ex- 

 perience we have already acquired, on this most important 

 branch of Horticulture, being of opinion that the different ap- 

 pearances, which they assume under different circumstances, 

 render it necessary to combine information from various 

 quarters, in order to attain a perfect knowledge of their na- 

 ture, and enable us to lay down such rules for their treat- 

 ment, as may be generally useful. 



As the Peach tree is one of the principal objects of garden 

 culture, I shall chiefly direct my attention to it at present. The 

 diseases which prove most fatal to it in this climate, are the 

 Mildew, Blight, and Gum ; respecting the nature of the first, 

 a variety of opinions have been entertained, and it has been 

 a question, whether it was of animal or vegetable origin, or a 

 fortuitous production ; but it is now generally admitted to be 

 a parasitic fungus, and that those parts of it which are appa- 

 rent, form the fructification. Its seeds, when mature, from 

 their extreme minuteness and levity, are dispersed to a consi- 

 derable distance in every direction, and such as happen to be 



