SECOND REPLY. 1?9 



extent in the year 1845, when it manifested itself with 

 equal formidableness in southern Sweden and in South 

 America, which two countries had been favoured (contrary 

 to what happened in central Europe) with remarkably fair 

 wheater. Besides, the Potato was not wholly exempted 

 from the evil by any position, any method of culture, or 

 in any variety, and this points out to us, at once, that the 

 actual cause of the disease must lie in a thorough degene- 

 ration of the plant, and not in any single external in- 

 fluence. If we ask how such a degeneration could have 

 occurred, the following considerations alone can guide us to 

 an answer. The wild Potato is a small, greenish, and 

 bitter-flavoured tuber, containing, however, a great deal of 

 starch. It is one of those plants which readily produce 

 varieties in cultivated soils, which exhibit tolerable perma- 

 nence when the conditions of culture remain exactly the 

 same. When this is not the case, new varieties arise, they 

 " sport" as it is called. The difference of these varieties 

 consists only in part in the far less essential alteration of 

 the form of the Potato, in its quicker or slower ripening. 

 Far more important is the difference in the chemical pro- 

 cess by which the relative amounts of starch and albumen 

 in the tuber become altered. Starch, a substance con- 

 taining no nitrogen, is the peculiarly characteristic consti- 

 tuent of the Potato, a substance which withstands decom- 

 position for a long time. The formation of this requires 

 the presence of a large quantity of potash, and therefore 

 the Potato belongs especially to the alkali-plants. Albumen, 

 on the contrary, rich in nitrogen, is particularly prone to 

 decomposition and rotting, and its presence, in large quan- 

 tity, renders the other substances also which can, alone, 

 long withstand decay, e. g. cellulose and starch, much 

 more liable to this process of solution. The production 



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