30 Diseases of the Potatoe. 



reds growing side by side appeared as fresh and fair as ever, 

 to a casual inspection. But on closer examination the 

 leaves at the bottom were dying, and the same process of 

 decay appeared to have commenced-, by which the pink-eyes 

 died. It is said the sap which forms the potatoe is elaborated 

 in the leaves, and I believe this is not doubted by any physi- 

 ologists; but how can this fact be reconciled with the fact 

 that some varieties are quite as large as usual, and the 

 assigned cause of rust we have mentioned. 



" From all the observations I could make there seems to 

 have been some general cause operating, from the time of 

 the blossoming of the earliest variety, and the earliest planted 

 to the latest, by which the formation of the bulbs was restricted 

 to few in number. This cause, I am constrained to believe, 

 is atmospheric." 



A work has lately been published by Dr. Van Martius, on 

 the epidemic diseases of potatoes. He enumerates all the 

 diseases that have been observed from time to time, and 

 describes more particularly two forms which did extensive 

 damage to the potatoe crops of Germany, in 1841. These 

 he calls, in literal English, stem rot, scab. It is to the first of 

 these diseases that we wish to call attention, as resembling, in 

 many of its symptoms, moist gangrene. There is, however, 

 this difference between 'that disease, and the one we are 

 about to mention, that the former attacked only leaves and 

 fruits, and was accompanied by the presence of a large quan- 

 tity of moisture, whilst this attacks the tuber, an underground 

 tem, and is characterized by a diminution of water in the 

 tissue of the plant. It is, in fact, a dry gangrene, and Mar- 

 tius calls it Gangrena tuberum Solani. 



When potatoes are attacked with this disease, the first 

 thing that is observed is, a drying up or shrivelling of the 

 tuber. The skin loses its ordinary lustre, becomes wrinkled, 

 and shows at last little irregular spots, of a dark brown color, 



