198 ON THE PREVENTION OF 



kept for the purpose of planting in the last spring. 1 inferred, con- 

 sistently with the hypothesis I adduced in the paper last quoted, 

 that the organisable matter these contained, being in a less firm and 

 concrete state, would prove more disposable, and that I might therefore 

 expect, in the succeeding season, plants of stronger growth, and more 

 smooth and perfect foliage. The result, in every respect, coincided with 

 my expectations; the plants presented the appearance of a different 

 variety, and afforded a more abundant crop and larger tubers than I had 

 ever obtained from the same variety. 



This experiment was confined to a single very early kind, which had 

 previously produced partially curled leaves ; but I imagine the same mode 

 of management will prove equally advantageous with other varieties which 

 show similar indications of incipient disease ; and as every improvement 

 in the culture of this plant, which can add to the produce without 

 increasing the ex pence, is of importance to the public, I submit the pre- 

 ceding account to the Horticultural Society. 



A very respectable writer, in the Memoirs of the Caledonian Horticul- 

 tural Society*, Mr. Dickson, has advanced an hypothesis, somewhat dif- 

 ferent from mine, respecting the curl in the potatoe : he conceives it to 

 originate in debility arising from the too great ripeness of the tubers, and 

 in the parent plant having too much expended itself in affording blossoms 

 and seeds, as well as tubers. But I can scarcely accede to this hypothesis, 

 because I do not think it probable that a plant, which is a native of 

 Virginia, can be over-ripened in the climate of Scotland ; and because 

 those varieties, which never afford either blossoms or seeds, have, in my 

 garden, been quite as subject to that disease as others. Mr. Dickson has 

 stated the curious fact (and I do not entertain the slightest doubt of his 

 perfect correctness), that a cutting taken from the extremity, which is 

 most firm and farinaceous, of a long, or kidney-shaped potatoe, will 

 afford diseased plants, whilst another cutting, taken from the opposite 

 end of the same potatoe, will produce perfectly healthy plants ; but I do 

 not attribute this to the greater maturity of the buds at the extremity, 

 than at the opposite end, for those nearest the parent plant are really the 

 oldest, the tuber being formed by a branch, which has expanded itself 

 laterally, instead of having extended itself longitudinally. Its buds are 

 in consequence arranged as they would have been upon the elongated 

 branch ; and every tuber, in its incipient state of formation, will extend 

 itself into a branch, as I have shown in the Philosophical Transactions 

 for 1809f, provided the plant, to which it belongs, be cut off close to the 



* See Vol. I. p. 50. f See above, p. 157. 



