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tlie infeft depriving the plant of part of its mucilage, 

 deranging its organization, and thereby preveiting 

 the juices from being properly fecreted, will perhaps 

 remain doubtful, and is of little confequence. 



When the vital principle is once become weakened, 

 or vitiated, the diforder may in fome potatoes be 

 continued longer, and in others be cured in a fliorter 

 time, according to the degree of the difeafe, the 

 ftrength of the ftamina, the foil into which they may 

 be tranfplanted, or the favourable or unfavourable 

 feafon for vegetation, which may immediately follow. 

 Thus, difeafed feed has fometimes been known to 

 produce a healthy crop, and fometimes a curled crop, 

 and that, perhaps, without receiving any frefli injury 

 from the bite of infers. From this caufe, however, 

 I have little doubt that the feed was firfl: vitiated ; 

 and I trufl: that the knowledge of this circumftancc 

 may be one flep towards the prevention or cure. 



It is now about feventeen years fmce I laid before 

 the Society my opinion on the caufe of the rot in 

 flieep, which is publiflied in the firfl volume of the 

 Society's papers. That fubjefl was then involved in 

 myflery, and my opinion was doubted and contro- 

 verted. The fociety is fmce fo well convinced of the 

 truth of it, as to have offered a premium for a more 

 perfeft knowledge of the genus and fpecies of the 

 infeft which occafions the difeafe, with the plant 

 Which it inhabits, and the bed method of extirpating 

 that infeft, or preventing ils deflruilive effefts in the 



animal- 



