26 Diseases of the Potatoe. 



the cause of the failure, permitting the potatoes they have 

 used for seed to become over-ripened, that the sets this 

 spring, to repeat again the words of Mr. Dickson, " did not 

 vegetate at all," even in the absence of heat and drought, and 

 in the presence of moist weather. Had the potatoes been a 

 little less over-ripened in 1842, the sets from them might 

 have produced only curl this season, though it is not improb- 

 able that the same degree of over-ripening may cause entire 

 failure now, that would only have caused curl years ago ; and 

 as over-ripening was excessive last year, owing to the v,ery 

 fine weather, so the failure is extensive in a corresponding 

 degree in this, even in circumstances considered by most 

 people preventive of its recurrence, namely, in cold and moist 

 weather. And observe the results of both 1842 and 1843 as 

 confirmatory of the same principle, illustrated by diametrically 

 opposite circumstances. The under-ripened seed of the bad 

 season of 1841 produced the good crop of potatoes in 1842, 

 in spite of the great heat and drought existing at the time of 

 its planting in 1842 ; while the over-ripened seed of the good 

 season of 1842 has produced extensive failure, in spite of the 

 coolness and moisture existing at the time of planting in 1843. 

 How can heat, drought, or fermenting dung, account for these 

 things ? 



As fact, may be mentioned the effects of comparatively 

 dry and moist soil, on cut sets and whole potatoes, which 

 were brought to light by an experiment of Mr. Howden, and 

 which obtained results no one would have anticipated. Says 

 Mr. Howden: 



" On the 28th of June I selected from a stock of potatoes 

 which had been repeatedly turned and kept for family use, 

 seventy tubers of the old rough black variety. I divided this 

 number into five lots, sizing them so that each lot of fourteen 

 potatoes weighed exactly four pounds. I made on that day one 

 lot of fourteen pounds into starch, and obtained nine ounces. 



