nn 



als 



of the 



Missouri Botanical Garden 



Vol. 10 FEBRUARY, 1923 No. 1 



POTATO BLACKLEG 

 WITH SPECIAL REFERENCE TO THE ETIOLOGICAL 



AGENT 1 



HARRY MILLIKEN JENNISON 



Professor of Botany, University of Tennesst • e 

 Formerly Assistant in Botany, Henry Shaw School of Botany of 



« Washington University 



Introduction 



The objects of the investigations presented herewith were 

 several, but only those outstanding should be mentioned at this 

 point. First of all, a determined effort was made to discover 

 the relationships, one to another, of the several "species" of bac- 

 teria recorded as being the cause of the blackleg disease of pota- 

 toes. To this end a thorough comparative study of the mor- 

 phology, cultural features, and physiology of some 12 strains of 

 the blackleg bacillus was made. The cultures employed rep- 

 resented strains of the organism from regions widely separated 

 geographically. Among them were the 4 "species" originally 

 described as being the cause of the disease in question. In the 

 prosecution of the problems arising the writer was led into a 



quantitative study of carbohydrate utilization by strains of the 

 blackleg bacillus and other microorganisms. The work done in 

 this connection constitutes an important phase of the investiga- 

 tions carried out. By way of extending the usefulness of the 

 paper, the writer presents a rather full and complete diagnosis 

 of the disease, with a discussion of the economic aspects, also a 

 revised description of the potato blackleg parasite. 



'An investigation carried out at the Missouri Botanical Garden in the Graduate 

 Laboratory of the Henry Shaw School of Botany of Washington "University, and 

 submitted as a thesis in partial fulfillment for the requirements for the degree of 

 doctor of philosophy in the Henry Shaw School of Botany of Washington Univer- 

 sity. 



(1) 



