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XIV. On the Prevention of the Disease called the Curl in the 

 Potatoe. By Thomas Andrew Knight, Esq. F.R.S. $c. 

 President. 



Read Feb. 2, 1813. 



Th e rough and uneven surface of the leaf, which in excess, 

 indicates, and indeed constitutes, the disease called the Curl 

 in the Potatoe, appears to exist in, and to form an essential 

 characteristic of, every good variety of that plant ; for I have 

 never found a single variety, with perfectly smooth and 

 polished leaves, which possessed any degree of excellence ; 

 and I have endeavoured to prove, in the Horticultural Trans- 

 actions of 1810,* that the .rough and crumpled state of the 

 leaf probably originates in the preternaturally inspissated 

 state of the fluid, in the firm and farinaceous Potatoe. Those 

 varieties are, however, generally most productive and grow 

 with the greatest luxuriance, of which the leaves are smooth 

 and polished ; and this point tends to prove, that the smooth 

 leaf is a more perfect and efficient organ than the rough 

 one ; the latter indicating some degree of approximation to 

 disease. 



I have stated, in the Horticultural Transactions of 181 l,t 

 that I obtained a second crop of Potatoes by planting those 

 of an early variety in the same soil from which a crop of the 

 same variety had been taken, in the month of July ; and that 

 I had employed, with success, the tops of those taken up, 

 with green fern and nettles, as manure. But I found the 



* See Vol. i. page 191. f See Vol. i. page 249- 



