310 . MAINE AGRICUETURAI. EXPERIMENT STATION. I909. 



trade is demanding seed not only pure and true to name but 

 also free from disease. 



The fact that most of the outbreaks occurred many miles from 

 the laboratory presented certain difficulties such that the organ- 

 isms associated with the disease were not isolated in pure cul- 

 ture till late in the summer of 1908 when the disease was defi- 

 nitely proven to be of a bacterial nature. The study of these 

 organisms is not completed, but certain facts of practical 

 importance to the seed grower have been ascertained. There- 

 fore it seems best to issue at this time a preliminary bulletin 

 upon the more practical phases of the subject as now known and 

 leave the more technical studies and final conclusions for a 

 later publication. 



Blackleg in America as is shown later, is a disease of more 

 than local distribution, doubtless occurring to some extent at 

 least over a considerable area of the potato growing sections in 

 Eastern United States and Canada. There is reason to believe 

 that it has existed in some localities for many years but it is only 

 very recently that it has been recognized and recorded m the 

 literature of American plant diseases. So far as the writer has 

 been able to determine the first mention of this trouble in this 

 country as a distinct disease W3.s when Jones recorded its occur- 

 rence in Vermont in 1906,* and described in some detail the 

 signs of the disease as it occurs in the field. Since its appear- 

 ance in every way agreed with the Schzuarzbeinigkeit, or "black- 

 leg" which he had studied in Europe t he used the same term as 

 a common name of the American form of the disease. The 

 writer was fortunate enough to see the field upon which Doctor 

 Jones based his description. Since the appearance of the dis- 

 eased plants as observed in Maine was identical with those seen 

 in Vermont and since the term "blackleg" is especially applica- 

 ble, suggesting the inky-black of the diseased stems it seems best 

 to continue the use of this term. 



Causal Organisms. 

 In July 1906 Harrison began the publication of a series of 

 articles upon "A Bacterial Rot of the Potato, Caused by Bacillus 



* Jones, L. R., Vt. Sta. Rept. 19, p. 257 (1906). 



fU. S. Dept. Agr., Bu. PI. Ind. Bui. 87, p. 17 (ipos). 



