344 [Senate 



Decomposed, 



Or third stage. The cuticle of the potato is now found wet and 

 flabby ; when ruptured, the pasty contents, or sloughy fluid, give off" a 

 very fetid odor. The organic structure is destroyed and microscopic 

 examination proves the existence there of myriads of animalculse. 



Scabby, 



Or fourth stage of the rot, is, properly speaking, the natural arrest, 

 or cure, of a local form of the disease. In this case, the remote.cause 

 of the disease, being weak in force, or of short continuance, or the 

 potato strong in vital staminas a local disease only had been pro- 

 duced, that extended no farther than the size of the scab, and was 

 arrested at the second, or fermentative stage of the disease, by the 

 evolution of the farinaceous, or starchy substance, that forms the 

 scab, leaving the remainder of the potato in sound and healthy 

 state. 



Cause. 



The cause of the " rot " is an epidemic condition of the atmos- 

 phere, brought into active influence by heat and moisture, and pro- 

 ducing the "rot" in the more tender varieties of the potato, or 

 those raised from diseased seed, or badly cultivated, or under any 

 circumstance unfavorable to their growth or preservation. 



Manner of attack. 



The disease frequently comes on suddenly, attacking and destroy- 

 ing the potatoes in whole fields or districts of country, within the 

 space of a few days. The roots and tubers of the potato first be- 

 come afiiected, and immediately the disease progresses until the 

 whole plant becomes diseased, the «talk becomes yellow, and the 

 leaves wither and curl. Carbonic acid gas is generated and evolved. 

 Fungous productions that live on decomposing vegetable substances, 

 are observed on the stem and leaves. Insects and animalculse are 

 found subsisting on all parts of the plant, now physically changed by 

 the fermentative effects of the disease. 



Illustration. 



The following case illustrates an attack of the epidemic form of 

 the " rot in potatoes," in Chester county, Pa., in 1843, and the mode 

 of farming, manuring and management, that has successfully over- 

 come the disease. 



