Abstracts. 313 



from different parts of Maine. For various reasons it was felt 

 that the name B. atrosepticus should be adopted for the group. 

 Two different cultures were obtained from Germany as Bacillus 

 phytophthoriis Appel but neither of these proved pathogenic. 

 In cultural characters they did not agree with each other nor 

 with Appel's original description of this organism. 



A FORM OF POTATO DISEASE PRODUCED BY 

 RHIZOCTONIA.* 



What appeared to be an undescribed type of potato tuber 

 disease was observed a few years ago in southern Maine for 

 the first time. While authors have described many troubles 

 more or less in association with Rhizoctonia, as far as the writer 

 was able to ascertain, outside of Maine, no other reference had 

 been made in the literature to this type of injury which the 

 writer chooses to call "dry core" of the potato tuber. 



Two phases of the disease are noted. First a stage which 

 on superficial examination might be mistaken for common scab. 

 Second, a stage showing a canal formation which might be 

 confused with the injury claused by the wire worm. 



In the first phase the fungus enters at the lenticels and 

 works its way down into the tuber without much external dis- 

 turbance. The definite boundary and dark brown color of the 

 area suggests a form of scab. The interior mass of hyphae, 

 broken-down cells and starch grains all remain in position, 

 forming a dry core. 



The second phase in this type of injury is found in the 

 older stage where the infected area reaches a greater diameter 

 than 3 mm. Owing to a drying out and shrinkage of tissues, a 

 pit or canal is formed in the center of the affected area. This 

 may present an appearance somewhat similar to wire worm 

 injury. 



The diseased areas are approximately circular in outline 

 and at the surface vary in size from that of a lenticel to 6 or 

 7 mm. in diameter. They usually extend into the flesh of the 

 tuber to a depth equal to or somewhat greater than the diameter. 



*This is an abstract of a paper with the same title, by G. B. Ramsey, 

 published in the Journal of Agricultural Research, Vol. IX, No. 12, 

 June 18, 1917, pp. 421-426 with 4 plates. 



