194 THE POTATO 



"5. The casual fungus is carried within the 

 tubers. 



"6. The internal infection is characterized by 

 brown or blackened areas usually in the vascular 

 ring; occasionally it specks the flesh in other areas. 



"7. Internally infected tubers are the chief 

 means of distributing the disease. 



"8. The presence of the disease in the tubers 

 may be made known by cutting knife sections from 

 the stem end. 



"9. The infection may be removed from 

 slightly infected seed by clipping away the stem 

 end and following by external treatment with 

 formaldehyde. 



"10. No attempt should be made to use deeply 

 infected seed, as the infection cannot be cut away. 



"11. Slightly infected seed will not materially 

 reduce the yield the first season. It is a means, 

 however, of infecting the soil, which may later 

 result in sick fields. 



"12. Spraying will not control the disease. 



"13. Proper storage prevents the progress of 

 the disease as a dry rot. 



"14. Careful inspection of the seed should be 

 made before placing it in storage. Cellar storage 

 under dwellings should be avoided when seed is 

 infected. Proper pit storage will give better re- 

 sults. 



"15. A seed plot on non-infected soil planted 

 with carefully selected healthy seed will offer a 

 means of getting a sound seed supply. 



"16. Sick fields should not be planted in po- 

 tatoes again for at least five or six years, and 

 even longer time may be required to work the 

 parasitic fungus from the soil. Grass and grain 

 crops will undoubtedly eliminate the fungus from 



