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 1s not doubted by any phy si- 
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 
stem, 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, 
