102 POTATO DISEASE. 



be untrue for this country, that no kind of potato is capable of 

 absolutely withstanding the disease. Those varieties, which from 

 the fact of being thick-skinned or deep-rooted, are less liable to de- 

 struction, do nevertheless succumb to the rot, under circumstances 

 that are eminently favorable to the development of the Peronos- 

 pora. 



The theory that the grape and potato disease is the result of a 

 stagnation of juices, resulting from cold damp, or hot damp 

 changeable weather, is as old as Hales and Parmentier. The idea 

 that it attacks some varieties more easily than others, because these 

 have become enfeebled by irrational culture, or by excessive tuber 

 propagation, has had its vigorous advocates in this country and 

 abroad. Both theories are wanting in any real support. The 

 stagnation of juices is a mere intangible fancy. No one can define 

 it. The circumstances which are said to produce it, often do not. 

 If a close steaming atmosphere stagnates juices, why are hot-beds 

 and hot-houses tolerated for an instant ? If stagnation induced in 

 enfeebled plants is the cause of the potato disease, why did not all the 

 old-fashioned enfeebled varieties suffer at once and equally ? If the 

 Mercer and Peach Blow are enfeebled, how is it that superb crops of 

 them are yearly obtained ? The " constitutional weakness " is sim- 

 ply a phrase, by the use of which we conceal from ourselves and our 

 neighbors the extremity of our ignorance. The sole evidence of 

 this weakness is the fact that potatoes rot. But if a variety is en- 

 feebled, the variety should perish, or if it is renewed by proper 

 treatment, it should then resist the disease. It is not physiological 

 to see a large crop of fine tubers one year, a crop of diseased ones 

 the next, and a large crop of sound ones the third year, propagated 

 on the same farm, from the same parent tubers, and of the same 

 enfeebled variety. 



Why should the enfeebling of hundreds of varieties of potatoes, 

 which for generations had invariably maintained their excellence, 

 and given satisfactory crops, have culminated in disease in the 

 year 1843 — the crops being still admirable as to quantity in that 

 very year ? 



Tiie theory that continued propagation from the tuber weakens 

 a plant, is not sustained by sxny direct observations or experiments, 

 but is arrived at in the following circuitous and illogical manner. 

 The fact is observed that potatoes rot, grapes mildew, and other 

 plants suffer from blight or rust. Without any adequate study of 



