1923] 



JENNISON — POTATO BLACKLEG 5 



culture of B. solanicola from Prof. L. R. Jones, to whom it was 

 given in Paris by Delacroix, but either it never possessed any 

 pathogenic properties, which is quite probable, or else had lost 

 them by cultivation." The same investigator made the follow- 

 ing statement, after having had opportunity to examine mate- 

 rial collected and preserved by Delacroix to illustrate the disease : 

 "It represents a fungous disease of the potato." 



Part III of van Hall's ('02) doctoral dissertation ("The stem 

 rot or blackleggedness of potato stems caused by Bacillus atrosep- 

 ticus nov. sp.") gives a fairly complete description of the disease 

 under discussion, together with a diagnosis of the etiological 

 agent sufficiently detailed and complete to enable one to classify 

 the parasite. For reasons which appear below, the writer is 

 of the opinion that the potato disease commonly referred to 

 throughout the United States and many parts of Europe as 

 "blackleg" is one and the same thing as that described by van 

 Hall. The etiological agent in all cases is probably identical and, 

 as far as is known, should be referred to van Hall's Bacillus 

 atrosepticus. 



At a slightly earlier date Appel ('02) published a short paper 

 ("Contribution to our knowledge of the bacterial rotting of po- 

 tatoes"), in which he described effects of the rot, also experi- 

 ments on the pathogenicity of the disease and stated that the 

 systematic position of the causal agent of the potato rot, as 

 well as its practical importance, would be given in a forthcom- 

 ing article. About a month later another short paper was pub- 

 lished by the same investigator (Appel, '02a), entitled "The 

 cause of the 'Blackleggedness' of the potato." In this article 

 he takes exception to Frank's binomial in the following words: 

 "Wenn nun auch der Frank'sche Name Micrococcus phytoph- 

 thorus auf den Bacillus nicht anwendbar ist, so glaube ich doch 

 aus praktischen Grunden den Speciesnamen beibehalten zu sol- 

 len, um so mehr als es sich herausstellte, dass eine ganze Reihe 

 von Pflanzen in charakteristischer Weise angegriffen wird. Ich 

 nenne daher den von mir isolirten Bacillus, welcher Schwarzbein- 

 igkeit und Knollenfaule bei den Kartoffeln hervorruft: Bacillus 

 phytophthorus Appel." Nowhere in this paper, however, is there 

 to be found a description of the morphological and cultural char- 

 acters (other than those implied by the name) of the etiological 



» 



which he had isolated. The binomial given by Appel 



this publication must therefore be regarded as a nomen nudum 



