268 Wisconsin State Horvicultukal Society. 



successive plantings from the germs raised from year to year 

 diminishing in vigor and productiveness, showing that a change 

 of conditions under which the plants are grown does affect their 

 constitutional vitality. 



The potato is a native of the high tablelands and mountainous 

 regions of South America and Mexico, where the soil is moder- 

 ately fertile, warm, light, and well underdrained, the climate 

 uniformly cool and comparatively dry, little subject to great ex- 

 tremes of temperature. In these conditions the potato is in its 

 natural habitat and makes a quick, steady, but moderate growth 

 of top and tuber. Droughts and extremes of heat seldom occur 

 to check its early maturity. M. Bousingault, in giving its history 

 in Bogota before its introduction into Europe, states that the 

 Peronospora infestans is also found there, but is powerless to injure, 

 on account of the vigor and uniform healthy growth of the plants. 

 It is with us, in the locations and in seasons where the conditions 

 are similar to those of its natural habitat, that the largest, the 

 finest and best crops of potatoes can be raised, and where alone 

 their cultivation can be made profitable. Great and sudden 

 changes of outward conditions are of themselves sufficient to pre- 

 vent that healthy development and perfect maturity upon which 

 vitality and productiveness depends, but when you add to these 

 an entire change of climatic conditions, and of the elements 

 and mechanical condition of the soil and the excessive stimulus 

 of high culture to an abnormal development of root and top, 

 it ceases to be a wonder that there is a loss of constitu- 

 tional vigor and hardiness, a predisposition to disease. In 

 causing an unnatural, an excessive development, or, as we call it, 

 in refining and improving the breed, both in animal and vegetable 

 life, we change the structure, the cellular tissues, making them 

 more dependent upon favoring conditions for their successful 

 growth, and also increase the liability to disease by lowering 

 their innate hardiness. Therefore it seems to us to be the most 

 natural conclusion that these unfavorable conditions to a perfect 

 hardy growth, both of the individual plant and of the species, are 

 the primary cause of the disease, and that the parasitic growth is 



