514 State Board of Agricultdue, &c. 



and the whole liistorj of the fungus now described is 

 re-enacted. 



Now that the entire life history of the potato fungus is 

 known it remains for practical men to turn these discov- 

 eries to account ; although their work is not the easiest and 

 most hopeful, they need not at least be led off on a wrong 

 track. The destruction of the res ting-spores suggests itself 

 as the most direct and certain way to hold the disease in 

 check. If this could be thoroughly effected, the disease 

 could hardly recur the succeeding year ; at least it may be 

 practical to prevent its having a strong start. To carefully 

 collect the diseased tops and tubers, and subject them to a 

 sufficient degree of heat would destroy the vitality of the 

 greater part of the resting-spores. When diseased pota- 

 toes are fed uncooked to animals, it is probable that the 

 resting-spores which they contain, will, from the firm and 

 close nature of their coats, pass uninjured through the stom- 

 achs of the animals, and be widely disseminated with their 

 excrements. By no means ought infected tubers to be used 

 for seed. The fact tliat the resting-spores winter securely 

 in the soil, teaches that land infested with them should not 

 be replanted to potatoes the following year. Land which 

 from having been often devoted to growing potatoes is una- 

 ble to yield large, healthy crops of this vegetable, — " potato- 

 sick soil," it is called in England, — has been observed by 

 most farmers of experience. A judicious rotation of differ- 

 ent crops, advisable in all cases, cleanses such land, as well 

 as returns to it some exhausted elements of fertilitv, and 

 enables it again to yield potatoes iu abundance. 



While making his observations, Mr. Smith found that 



