1923] 



JENNISON — POTATO BLACKLEG 7 



Appel's original culture. Smith states in this article that he re- 

 gards Bacillus solanisaprus Harrison as closely related to, but 

 not identical with, B. phytophthorus Appel. 



About the same time Pethybridge and Murphy ('10) pub- 

 lished a note on a bacterial disease of the potato plant, attrib- 

 uting it to a new species of bacterium for which they proposed 

 the name "Bacillus melanogenes." In 1911 these investigators 

 published a full account of the malady referred to above, to- 

 gether with a complete diagnosis of the etiological agent. The 

 potato disease described by them was probably none other than 

 the "blackleg," and there is very little, if any, doubt in the writ- 

 er's mind that their Bacillus melanogenes should be referred 

 to Bacillus atrosepticus van Hall. 



Murphy ('16) gives an account of a blackleg disease of po- 

 tatoes occurring in Canada, attributing the disease to Bacillus 

 melanogenes Peth. & Murphy. 



From a series of observations made in 1916, Morse ('17) re- 

 ports having seen potato blackleg in certain of our western states, 

 though he found it to differ in certain respects from that familiar 

 to him in Maine. This paper is an important contribution to the 

 literature of the subject. Of particular significance are his com- 

 parative studies of the causal organisms. The writer is in ac- 

 cord with Morse's conclusion that the strains studied (including 

 cultures "received under the names 'Bacillus atrosepticus van 

 Hall,' 'B. solanisaprus Harrison,' and 'B. melanogenes Peth. & 

 Murphy','' as well as 3 isolated from blackleg material in Maine) 

 are identical. However, since Morse was unable to procure a 

 trustworthy culture of B. phytophthorus Appel he presents no 

 data which "bear on the relationship between the organism orig- 

 inally described by Appel as B. phytophthorus and the other 



blackleg bacteria 



f 



Smith ('10) that B. phytophthorus Appel is not identical with 

 B. solanisaprus Har., Morse was forced to exclude it from B. 

 atrosepticus van Hall. This is most regrettable, since Morse 



small differ 



bacteria 



not sufficient for the establishment of new species. His work 

 shows abundant evidence of having been carefully done. Un- 

 fortunately, there seems to be no record of the comparative stud- 

 ies upon which Smith ('10) bases his opinion. 



Paine C17) referred to the cause of the potato blackleg studied 

 by him in England as Bacillus atrosepticus van Hall and ex- 



