542 BOARD OF AGRICULTURE. [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 be 

 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 affected. 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 

 favoral)le 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 thi;^ subject of inquiry. 



