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II. Upon the Causes of the Diseases and Deformities of the Leaves 

 of the Peach-Tree. By Thomas Andrew Knight, Esq. 

 F.R.S. Pres. 



Read July 15, 1834. 



I communicate the following facts without venturing to draw any 

 conclusions, being wholly unable to trace any connection between 

 the apparent cause and the apparent effect; and I should have 

 waited till I had obtained the evidence of more experiments, but 

 that the evidence of such experiments, confined to a single situation 

 or soil, would have still remained defective. 



Every gardener knows that the leaves of Peach-Trees frequently 

 become diseased and deformed, owing to the operation of two per- 

 fectly distinct causes ; one being obviously the depredations of 

 insects, and the other being generally, I believe universally, supposed 

 to be frost. In the last mentioned case, the leaves, if suffered to 

 remain upon the trees, continue to grow, and in part to perform their 

 office of generating the living sap of the tree ; but the whole, or 

 nearly the whole, of the fluid thus created is expended in their own 

 deformed and morbid growth. In unfavourable situations, such as 

 mine unfortunately is, a large portion of the first formed leaves is 

 frequently rendered useless, or worse than useless ; and I do not re- 

 collect a single season in which a very large part, and sometimes all 

 the early foliage of my Peach and Nectarine trees, which almost 

 wholly occupy the entire south wall of my garden here, ( Downton 

 Castle) has not been destroyed or rendered useless, previously to 

 the present season. 



In the autumn of the year 1831 a small Nectarine tree, which 

 grew in a pot in my Peach house, was removed from it, and planted 



