26 Diseases of the Potatoe. 
fhe cause of the failure, permitting the potatoes they have 
nsed 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-Tipening was excessive last year, owing to the very 
fine weather, so the failure is extensive in a corresponding 
depree 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 1848. 
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: ° 
“Qn 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. 
