324 MAINS AGRICULTURAL EXPERIMENT STATION. I907. 



these external symptoms mentioned might result from any other 

 cause which injured the stem near or just below the surface of 

 the ground and thus interfered with the free transference of 

 nutrient substances. 



Examination of the diseased plants showed that in every 

 instance the stem was more or less blackened or browned 

 usually at or just below the surface of the soil and downward. 

 At Sherman, however, a few specimens showed the blackening 

 following up the main stalk and branches for several inches. 

 Frequently the diseased portions of the stem were very soft, 

 resembling the decay caused by soft rot bacteria, while other 

 cases, possibly in the later stages, showed more of a dry rot. 

 In every case where the seed tuber could be found it was soft 

 and mushy as though attacked by a soft rot. The seed tubers 

 of healthy potatoes were, as a rule, sound and remarkably well 

 preserved. 



Another field at Sherman, about a mile from the first, con- 

 tained from 5 per cent to 15 per cent diseased plants, the higher 

 percentage being on the more poorly drained portions of the 

 field. A few fields were found at Houlton where diseased 

 plants were quite frequent, but here as in some other places a 

 careful search over any large field would occasionally produce 

 isolated plants which were affected. Late in the season out- 

 breaks were discovered at Dover and at Orono. At the former 

 place was secured the only evidence of possible spreading of 

 the disease in the field. Here the portion involved was situ- 

 ated in a somewhat depressed area in an otherwise well-drained 

 field. The owner, a professional man, had had the matter 

 under observation for some days before the. field was seen by 

 the writer. He was well satisfied that the diseased area was 

 gradually enlarging. In fact when the field was visited the 

 plants on the margin of the somewhat circular, diseased area 

 showed earlier stages of the disease than those in the center. 

 In all other cases examined there did not appear to be any 

 evidence of spreading from plant to plant or from hill to hill. 

 If 2 diseased stalks were close together it was invariably founa 

 that they arose from the same seed piece. 



The case at Orono would indicate that the disease is trans- 

 mitted with the seed. Here all the seed on a 4-acre field was 

 obtained from away, and from 3 or 4 different sources. Two 



