218 AGRICULTURAL EXPERIMENT STATION. [Jan. 



distinct advantage in this respect noticeable for either 

 method of planting. 



5. The free use of coal ashes in the drill, which was 

 tried by request, had no observable influence on the devel- 

 opment of scab in the present case, although it has been 

 thought by some to favor its development, and others have 

 regarded it as a preventive. 



6. The thicker-skinned and red-skinned varieties show 

 no greater resistance to scab than others ; our best results 

 this season were from light-skinned and rather delicate, 

 fine-grained sorts. These results conflict with some rather 

 general beliefs, but they are the outcome of experiments 

 carefully planned and carried out, and involve no inherent 

 improbabilities. 



The results of extended studies as to the cause of potato 

 scab have lately been published by Mr. H. L. Bolley.* 

 He believes it to be due to the action of a Bacterium which 

 lives in the soil, and can live parasitically on the potato 

 tuber, causing; an irritation which results in the formation 

 of the scab. Mr. Bolley's experiments were well planned 

 and apparently carefully conducted, and his results are of 

 much value. The scab produced by him was apparently 

 the form first called by the writer in the last report of this 

 station the "surface" form. In Bulletin No. 105 of the 

 Connecticut Agricultural Experiment Station, Dr. Roland 

 Thaxter has announced the results of some investigations, 

 in which he had obtained, from potatoes affected by the 

 "deep" form of scab, a vegetable organism of doubtful 

 relationships, which, when sown on growing potatoes, 

 reproduced the same form of the disease in a striking man- 

 ner. 



In our own microscopic study of scabbed potatoes, bac- 

 teria were, of course, constantly met with, and fungus 

 threads occasionally, but never under such circumstances 

 as to raise any serious suspicion of their causal relation to 

 the trouble. Had such a suspicion been raised, however, 

 it would have been impossible to have demonstrated the cor- 

 rectness or falsity of the view, since the Department had then 



* Agric. Science, September and October, 1890. 



