PREFACE. 



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

 of Koch, Init until recenth' our knowledge of it has been in a \'er)' chaotic state, it 

 having been for the most part for twent)'-five years a recognized ]nit uncultivated 

 field. In recent years, however, publications on plant liacteria haA'e multiplied, 

 and they now amount to several hundred titles. 



The writer's studies of the bacteria themsch-es and of the diseases which the}' 

 cause, as distinct from the literature of the subject, began in iy93. At that time 

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

 more extensive, but it is nowhere gathered together in one place and proper!}- sum- 

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

 treatise here presented might be clarif}'ing and useful to niau}- people. There have 

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

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

 the requirements of modern pathological inqnir}- that this whole sulyect has been 

 brought into disrepute. This is the only possil^le exjilanation of the fact that up 

 to a very- recent date writers on pathology and bacteriolog)' ha\'e been telling their 

 readers that there is no good evidence of the existence of an}- such diseases. 



The following editorial paragraph from the Jiolauical Gazette, Fel^ruar}-, 1S93, 

 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 continnoiis and 

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

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

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

 laboratory study, would be helpful, if well done. 



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

 multiplication of literature is shown b}' 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 difBculties 

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

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

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

 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 uncertaiut}' that the writer began his stud}- 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 



