"THE POTATO DISEASE." 56 



and thence descends to the tubers ; in all cases it is accom- 

 panied by a peculiar parasitic fungus the Botrytis infes- 

 tans which, under certain conditions of the atmosphere, 

 frequently spreads it rapidly over the stem and leaves, and 

 induces a rapid decay. On examining a tuber from the de- 

 cayed stem, a discoloration of its tissues will be noticed ; 

 and if the disease is far advanced, they will have become 

 so far disorganized as to have lost their normal form and 

 assumed a pulpy condition, emitting an ammoniacal odour, 

 more or less strong and fetid. The portion of the tuber 

 thus affected is of course unfit for food; if the sound parts 

 be not at once separated they become rapidly inoculated, 

 and the whole is lost. 



The disease has generally been noticed as making its 

 appearance in the first or second week in August; and 

 Mr. Berkeley tells us that " if we then carefully examine 

 the crop, we may find some of the plants with small 

 brown patches on their leaves and stem, surrounded by a 

 paler ring, the whole of which is frosted with Botrytes. If 

 the weather be dry the progress of the disease is very slow ; 

 but if a moist, warm day intervene, an accurate observation 

 of the same speck, at different times even of the same 

 day, will show that the mould spreads with great rapidity, 

 destroying all before it, or converting the green cells into 

 brown. The separate spots soon become confluent, the 

 evil extends to the stems, and, if the weather be favourable 

 to its progress, in a few days the whole becomes corrupt 

 and putrid/ 7 At this period of the season the electric con- 

 dition of the atmosphere is frequently in a disturbed state, 

 and we have thunder-storms, accompanied by heat and 

 heavy rains. These conditions are eminently favourable 

 to the development and spread of the disease, and have 

 given rise to a very general, though at the same time very 

 erroneous opinion, that electricity is the actual cause of it. 

 In regard to the remedies recommended, the old proverb, 



