190 VEGETABLE GARDENING. 



a crop of smooth, clean potatoes, no matter what may be the 

 character of the soil; but apparently clean seed potatoes may 

 have the germs of the scab fungus on their surface. This is 

 often the case where they have been sorted out from a lot 

 that is somewhat infected with scab. In this latter case the 

 tubers should, at least, be thoroughly washed in running 

 water to remove any germs that may be present or, what is 

 better yet, be treated with corrosive sublimate (mercuric bichlor- 

 ide ) as recommended below. 



Land infected by the germs of potato scab will produce a 



Treated. Fig. 100.— Potato Scab. Not treated. 



Both plates grown from the same lot of scabby seed. 



more or less scabby crop, no matter how clean and smooth the 



seed used. 



Scabby potatoes should be dug as soon as mature, since 

 the scab fungus continues to grow on the potatoes as long as 

 they are in the ground. 



Scabby potatoes may safely be used for seed, providing 

 they are first treated with corrosive sublimate as follows: 

 Procure from a druggist two ounces of powdered corrosive 

 sublimate (mercuric bichloride); put this into two gallons of hot 

 water in a wooden or earthenware vessel and allow it to stand 

 until dissolved. Place thirteen gallons of water in a clean 

 barrel, pour in the solution of corrosive sublimate and allow 

 it to stand two or three hours, with frequent stirrings in order 

 to have the solution uniform. Select potatoes as nearly free 



