PREFACE. 



The subject of bacterial diseases of plants is older than the poured-plate method 

 of Koch, but until recently our knowledge of it has been in a very chaotic state, it 

 having been for the most part for twenty-five years a recognized but uncultivated 

 field. In recent years, however, publications on plant bacteria have multiplied, 

 and they now amount to several hundred titles. 



The writer's studies of the bacteria themselves and of the diseases which they 

 cause, as distinct from the literature of the subject, began in 1893. At that time 

 there was very little reliable information on this subject. The literature is now 

 more extensive, but it is nowhere gathered together in one place and properly sum- 

 marized. It has seemed, therefore, for a long time, that a work of the scope of the 

 treatise here presented might be clarifying and useful to many people. There have 

 been published, and are still appearing, so many papers on the subject of bacterial 

 diseases of plants by writers ignorant of bacteriological methods and indifferent to 

 the requirements of modern pathological inquiry that this whole subject has been 

 brought into disrepute. This is the only possible explanation of the fact that up 

 to a very recent date writers on pathology and bacteriology have been telling their 

 readers that there is no good evidence of the existence of any such diseases. 



The following editorial paragraph from the Botanical Gazette, February, 1893, 

 may be cited as indicating the general feeling on this subject at that date: 



What is especially needed at this stage of advancement is the cpntinuous and 

 systematic examination of the whole ground by one or more well-equipped investiga- 

 tors, and the publication of a critical statement of what may be safely accepted as 

 proven. Even a summarization of the present status of the subject, without critical 

 laboratory study, would be helpful, if well done. 



That this feeling has become intensified with the progress of time and the 

 multiplication of literature is shown by the following citation from the large Treatise 

 on Bacteriology, by Miquel and Cambier, published in 1902: 



The list of bacteria capable of attacking the higher plants increases rapidly from 

 day to day ; but whether the experiments of plant pathology offer greater difficulties 

 than those of animal pathology, or whether the authors who have undertaken them 

 have ignored the multiple resources which bacteriology offers to-day, many of the 

 species described must be studied anew, their monography offering regrettable lacunae. 

 By the side of some fruitful and well-conducted labors we find, unfortunately, alto- 

 gether too many which must be done over entirely. 



It was with the hope of making useful discoveries and clearing up part of 

 this contradiction and uncertainty that the writer began his study of this class of 

 diseases. His first effort in the way of preparation was to supplement his botanical 

 training with a knowledge of bacteriological methods which he obtained from 

 standard literature and competent teachers. His second effort was to gather 



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