1890.] PUBLIC DOCUMENT — No. 33. 221 



words " scab," " Schorf " and " Skurv " are not terms which 

 mean only definite things, but are of popuhir and general 

 application ; and the assumption that they are used in 

 different countries to designate the same disease, remains 

 merely an assumption until it is proved by direct comparison 

 to be correct. Indeed, the assumption that the word " scab" 

 is used, throughout our own country, for the same affection, 

 is, perhaps, hardly justified ; but, as it is borne out by 

 specimens from various parts of New England, its correct- 

 ness for the whole country is taken for granted. In order, 

 however, to settle the uncertainty whether the three words 

 above quoted are synonymous, two leading writers on the 

 subject were requested to furnish material for comparison 

 with American scabby potatoes. Dr. Sorauer, director of 

 the experiment station at Proskau, Germany, was asked to 

 send potatoes affected with the disease known in Germany 

 as " Schorf" or " Grind,"' and Dr. Brunchorst of Beriren, 

 Norway, to send potatoes attacked by the disease known in 

 that country as " Skurv," and said by him to be caused by a 

 species of slime mould. Both very kindly responded, and 

 the Avriter wishes here to extend to both botanists his very 

 sincere thanks for their interest and assistance. 



Dr. Sorauer sent several tubers affected with what, to the 

 naked e3^e, resembles in all respects our superficial form of 

 scab ; and microscopic examination fully establishes its 

 identity with our disease. The accompanying Fig. 3 is 

 made from a photograph of one of the potatoes sent by Dr. 

 Sorauer. The German " Schorf " and the Eng^lish " scab " 

 are, then, synonyms, as applied to diseases of the potato. 



From Dr. Brunchorst, a photograph of tubers attacked 

 by "Skurv" has been received; but, unfortunately, the 

 specimens of such tubers, promised by him, have failed 

 to arrive, and it is impossible to accurately compare the 

 disease with our own. Such comparisons as are rendered 

 possible by Dr. Brunchorst's descriptions and figures and 

 by the photograph he has had the goodness to send, 

 point, however, to the conclusion that he is dealing with 

 a disease very distinct from the scab, and that his assump- 

 tion that the American and German diseases are identical 

 with the Norwegian, is incorrect. 



