54 Forty-third Annual Report on the 



shown to indicate that if the foliage of the potato plant is kept 

 whitened with the Bordeaux mixture it can be kept free from the 

 fungus. 



To try the effect of deep planting on the productive power of 

 the potato, a trench about a foot deep was dug and 12 tubers 

 planted in it about a foot apart. These were covered about four 

 inches deep. At the same time 12 tubers were planted about 

 four inches deep in a row by the side of the trench. As the 

 plants in the trench grew, soil was, from time to time, thrown into 

 the trench till it was filled. In all other respects the two experi- 

 ment rows received the same treatment. The plants in the 

 trench were more productive than those planted in the ordinary 

 way, yielding 198 tubers weighing 19| pounds ; the others yield- 

 ing 155 tubers weighing 14 pounds. But the trench system 

 proved superior not only in its greater production, but also 

 in its better protection. Among the tubers dug from the 

 12 hills in the trench, four were found affected by rot, and 

 these all occurred in two hills. But among those dug from 

 the 12 hills planted in the usual way, 37 affected ones were 

 found, nearly every hill furnishing some. Thus it is evident 

 that deep planting is a protection against rot. The spores 

 produced by the fungus on the leaves are the cause of the 

 mischief in the tuber. They fall to the ground and are washed 

 down through the soil to the tubers by the rain. They do not so 

 easily reach the tubers when they are covered by a thick layer of 

 earth as when they lie near the surface. It also follows that a 

 very compact soil affords greater protection than a loose porous 

 one, though it is not as favorable to production. In a part of the 

 garden the soil was of such a character that the heavy rains had 

 made it very firm and compact. It was scarcely possible to dig the 

 tubers with the implements ordinarily used for this purpose because 

 of the hardness of the soil. Although the vines here had been badly 

 affected and speedily killed by the fungus no rotten tubers were 

 found. The spores, which must have been very plentiful here, were 

 prevented from reaching the tubers by the hard and compact condi- 

 tion of the soil over them. These two examples indicate the way in 

 which the germs of the disease chiefly reach the tubers. Any 

 practical method of preventing them from being washed down 

 through the soil to the tubers will solve the problem of saving 

 them from this infection. But it is far better to strive to pre- 



