184 7.J Potato Disease. 77 



POTATO DISEASE. 



Notwithstanding the theme has been long a standing one, still 

 it may yet be regariled as a topic of great interest to the agricultu- 

 rist and physiologist. To the first it is interesting practically, and 

 to the latter theoretically. To the first preventions are important, 

 as it forms a necessary and essential part of his resources. 



At this late day we have no occasion to describe in full the 

 progress of the disease. In general it involves in destruction the 

 stalks and tubers; though it is not always the case that the forrner 

 perish. In its most malignant form, they are speedily killed. But 

 potatoes, during the first years of its attacks, rotted after they were 

 housed. There were, however, indications of disease upon them 

 when raised from their hills. 



Our own observations, in conjunction with Mr. Salisbury, prove 

 conclusively that the disease begins with the lowest part of the 

 stem. It appears first softened just beneath the cuticle, at the 

 points where the fibres start out just above the attachment of the 

 old or seed potato. From this point it proceeds upward, involving 

 the cellular tissue of the stem. The circulation gradually dimin- 

 ishes, and the leaves soon dry upon their edges. This is succeeded 

 by the death of the edge of the leaf fiist, and then the whole stalk; 

 the terminal part, with its leaf, being the last which dies. 



Our object in calling up this subject again to the notice of 

 farmers and others who feel interested in it, is to request them to 

 observe one fact, viz., the temperature of the hills or ground in 

 which the potatoes are growing. There is no cause, perhaps, 

 more influential in producing the decay of organic substances, than 

 heat. This is especially the case when the thing is buried, or 

 charged with water. It is easy to see that potatoes, or any im- 

 mature or over-ripe fruit, when subjected to a certain tempera- 

 ture, would necessarily undergo changes which in the end must 

 result in its total decomposition. This temperatuie comes within 

 the range of that which may be produced by the sun. In many 

 instances the evaporation or exhalation of the water is so rapid 

 that the plant is unable to obtain a supply of water through the 

 roots; the consequence of which is, that it withers, and in some 

 instances dies. In a potato field where the tops have been de- 

 stroyed and the hills are exposed to the direct rays of the sun, the 

 temperature of the ground is elevated higher than is consistent 

 with the health of the growing crop. A continuance of such a 

 state for days in succession could scarcely occur without leaving 

 a predisposition at least to decay, if it did not at once make a 

 visible impression upon it. Without resorting, then, to a cause 



