136 AGRICULTURAL EXPERIMENT STATION. [Jan. 



globular and separate, as in Plasmodiophora. In Fig. 3 

 are shown the active and resting stages of the latter, and 

 Brunchorst's representation of the resting state of his sup- 

 posed scab parasite. 



Both the New York and the Massachusetts observations, 

 before referred to, bear on Brunchorst's views. If the scab 

 is caused by a living organism, its development must bo 

 checked by the application of substances fatal to parasitic 

 forms of life ; and scabby potatoes would be expected to 

 produce usually a scabby crop, when planted, the infected 

 tubers infecting the new generation. Experiments with 

 fungicides, at both stations named, gave only negative re- 

 sults, the decrease in scabbiness where they were used being 

 insignificant. The average proportion of scabby tubers pro- 

 duced from scabby '< seed " in the New York experiments 

 was forty-five per cent , while smooth ' ' seed " yielded 

 thirty-seven per cent, of diseased potatoes. At our own 

 Station the crops have varied little in quality, when raised 

 under similar conditions, whether from smooth or scabby 

 " seed; " and badly diseased tubers have, in several cases, 

 produced exceptionally good crops. 



One further observation, noted by Beckwith in the report 

 quoted, is of interest. He finds that, while forty-three per 

 cent, of the white-skinned potatoes and fifty-three per cent, 

 of the flesh-colored ones raised on the station farm were 

 scabby, only twenty-seven per cent, of the dark-skinned 

 ones were aflected. Assuming the cause of the disease to 

 be external to the tuber, such a result was to be expected. 



From the above statement, it is evident that much re- 

 mains to be learned before our knowledge of the cause of 

 the potato scab will be at all satisfactory. And, until a 

 pretty definite knowledge of its cause is gained, all attempts 

 at discovering a remedy are so many leaps in the dark. 

 The conditions at this Station are in many respects very 

 favorable for a hopeful prosecution of investigations into the 

 nature and origin of the pest, which are planned for the 

 coming season. The writer will be very glad of suggestions 

 or reports* of experience from persons who have had to do 

 practically with the disease, or to communicate with any 

 who are interested in this subject of inquiry. 



