270 Wisconsin State Hoeticuxtueal Society. 



seasons adapted to the growth of the fungus, such is the rapid 

 development of the spores, that the few or many destroyed will 

 make practically little difference in their numbers. 



The selection of early varieties, and of those kinds that are the 

 least liable to be affected with the rot, is recommended as benefi- 

 cial. Also early planting, may ensure the ripening of the tubers 

 before the disease usually makes its appearance, and if they are 

 harvested at once, and stored in some cool, dry place, the crop 

 will be secured. 



Drawing up the earth around the hill early in the season, giv- 

 ing It the form of a sharp ridge, with four or five inches of soil 

 over the growing potatoes, is confidently announced by some as a 

 sure preventive. The experiments reported seem to indicate 

 that this greatly reduces the number of diseased tubers. Those 

 who recommend this treatment claim that the protection is given 

 by the thickness of the earth over the tubers preventing the 

 spores from washing down through the soil to them, where they are 

 supposed to germinate and penetrate to the interior, and also that 

 the form of the hill carries the spores, as they fall from the leaves, 

 away from over the tubers, and they are then washed by the rains 

 into the furrows. This explanation can hardly be the correct one. 

 Those who have studied the growth of the fungus most thor- 

 oughly hold that the spores do not and cannot enter the tuber 

 either before or after germination through the skin, but only 

 through the leaves, and that, too, through the breathing pores on 

 the underside of the leaves. In fact no evidence has been dis- 

 covered that they can enter the potato direct where the skin is 

 unbroken and sound. The beneficial results frpm this treatment 

 may, and probably do, come from the protection given to the plant 

 from heat, moisture and other injurious climative influences. 

 The covering over the roots tends to keep them cool, giving them 

 greater power, the sharp pitch of the hill turns off excessive moist- 

 ure, and the necessary furrow between the rows gives the plants 

 thorough drainage, so that the conditions for growth are favorable 

 and a strong, healthy growth throughout the season is secured. In 

 thus adapting outward conditions and culture so as to secure a 

 hardy, mature growth seems to be the best remedy, the most 

 effectual method of preventing this disease. 



