THE PAGE OF NATURE. 



273 



nected with the disease, and is found on the decaying 

 plants ; the growth of the fungus being probably aided 

 by some predisposition in the state of the vegetable, in- 

 duced by the soil or the atmosphere. The epidemic was 

 not confined to the potatoes grown in this country, but 

 seems to have prevailed throughout the world, attacking 

 indiscriminately all the cultivated varieties, as well as 

 the wild plants in their original centre of distribution, the 

 lower mountain plateaus on the western coast of South 



FlG. 39. BOTRYTIS INFRSTANS. 



(1.) Young plants ; (2.) Full grown; (3.) Spore. All magnified. 



America. This singular fact, while it shows that neither 

 the soil, climate, nor mode of farming in this country 

 was the sole cause, clearly establishes the vegetable 

 origin of the disease. It may be remarked that the 

 potato is commonly attacked after the tubers have been 

 formed, and have attained a considerable size. The 

 leaves are usually the first parts affected, becoming 

 tinged with a bluish -brown spot on the under side ; and 

 from thence it spreads rapidly down the stem, till in a 

 very short time the whole of the plant above ground is 



