Family Solanaceae 319 



or spores. The filaments or gonidia are non-motile. 

 It produces no gas, but is capable of producing a 

 brown pigment which is soluble and diffuses through 

 the medium. 



Control. The disease is carried about with infected 

 tubers. The latter when fed to cattle will infect the 

 manure. The scab organism can pass the digestive 

 tract of the cows or horses without losing its vitality. 

 Before planting, seed potatoes should be disinfected 

 with corrosive sublimate or f onnaldehyde. See also 

 p. 336. Fertilizers which tend to make the soil alka- 

 line, such as barnyard manure, lime, wood ashes, or 

 bone meal, aU tend to increase scabby potatoes. Tlie 

 use of kainit, muriate of potash, sulphur, or acid 

 phosphate a/a fertilizer all tend to decrease scab. 



Black Wart 



Caused by Chrysophylyctis endobiolicvm (Schilb.) 

 Perc. 



Black wart is perhaps one of the most dangerous of 

 the potato diseases. The trouble is now prevalent 

 in Germany, England, Upper Htmgary, and in New- 

 foundland. The disease has not as yet made its 

 appearance in the United States, although it is 

 believed that infected potatoes have been shipped in 

 from Newfoundland. 



Symptoms. In early stages of infection, the eyes 

 are first attacked, turning brown and later black. 

 The disease then works down to the tuber, which 

 is but slightly disfigured. In advanced stages, big 



