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Dr. Smith's studies of the bacterial organism eausintj the black or 

 brown rot of turnips dealt with in this paper were begun in September, 

 1890. In other papers he has discussed the morphology and cultural 

 peculiarities of the parasite and has pointed out methods for limiting 

 the spread of the disease. In this paper he contines his attention to 

 the action of the parasite on the host plant, demonstrating l)y means 

 of the microscope and camei'a the a))ility of the organism to destro}'^ 

 cell walls, and illustrating \arious stages in. the progress of the disease. 

 The paper is timely in that the tibilit}- of bacteria to destroy cell walls 

 in living plants is still disputed in many quarters and is a subject left 

 untreated in most of the text-books. 



The paper is technical and is designed for the use of investigators 

 in plant pathology. 



Albert F. Woods, 

 Pathologid and Physiologist. 



Office of the Pathologist and Physiologist, 



Washington.^ D. C, October 6., 190°2. 



