VII. THE BACTERIAL BLACK ROT OF THE POTATO 



{Syn. Black leg, Basal Stem-rot and Tuber-rot) 



Type. — This is a wide-spread and very destructive soft rot 

 of the potato and some other plants. Vessels are sometimes 

 occupied, but it is a disease of the parenchyma rather than of 



Fig. 190. — Curling of potato leaflets due to Bacillus phytophthorus (Appel I). 

 Spring of 1915. Second set of needle-prick stem inoculations. 



the vascular system, being found, according to Dr. Appel, only 



occasionally and exceptionally in the vessels of the potato plant. 



The first above-ground signs of the disease are either sudden 



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