Diseases of the Potatoe. 23 



each tuber had emitted shoots of three or four inches long. 

 They were then carefully- detached with their fibrous roots, 

 from the tubers, and were committed to the. soil ; where 

 having little to subsist upon except water, I concluded tho 

 cause of the disease, if it were the too great thickness of the 

 sap, would be effectually removed, and I had the satisfaction 

 to observe, that not a single curled leaf was produced ; though 

 more than nine-tenths of the plants, which the same identical 

 tubers subsequently produced, were much diseased. 



In the spring of 1808, Sir John Sinclair informed me that 

 a gardener in Scotland, Mr. Crozer, had discovered a method 

 of preventing the curl, by taking up the tubers before they 

 are nearly full grown and consequently before they became 

 farinaceous. Mr. Crozer, therefore, and myself, appear to 

 have arrived at the same point by very different routes; -for 

 by taking his potatoes, whilst immature, from the parent stem, 

 he probably retained the sap nearly inthe state to which my 

 mode of culture reduced it. I therefore conclude that the 

 opinions I first formed, are well founded, and that the disease 

 may be always removed by the means I employed, and its 

 return prevented by those adopted by Mi*. Crozer. 



Another disease affects the seed, and is called the failure, 

 or taint, which consists of the destruction of their vital pow- 

 ers. Many conjectures have been hazarded as to the cause 

 of the failure, and most of them have ascribed it to the fer- 

 mented state of the dung, to the drought of the season, to the 

 heating of the sets, to the tuber being cut into sets, and o^her 

 secondary causes ; but all these conjectures leave untouched 

 the principal consideration* in the question, how these cir- 

 cumstances should induce failure now, and not in by-gone 

 years. Cut sets have been used for many years without- 

 causing failure. Farm-yard dung in various states of de- 

 composition, has been used as long for raising potatoes. The 

 extraordinary drought of 182G caused no fa'.lure, while in 

 comparative cool seasons the disease has made great havoc. 



