ATTITUDE OF PATHOLOGISTS AND BACTERIOLOGISTS. 1 9 



yellow disease of beets, grease spot of beans, gangrene of potato, etc. The text is very- 

 brief and closely follows Prillieux, except in case of the spot disease of beans, which is 

 based on Delacroix's own work. 



In the second revised edition of his large Text Book, issued in 1901, Dr. Sternberg 

 mentions bacterial plant diseases for the first time, devoting 7 pages to the subject, quoting 

 exclusively from the publications of Smith and Waite. 



Chester's book (1901) includes descriptions of a few plant parasites, but does not 

 venture any statements as to pathogenesis. 



In their large Treatise published in 1902, Miquel and Cambier devote 10 pages out 

 of 1059 to the micro-organisms of plants. They mention 28 species as being of more or less 

 interest in this connection. For general remarks by these authors on the uncertainties 

 hanging over this subject, see citation in the preface to vol. I. 



Van Hall's Thesis (1902) maintains the existence of bacterial diseases as proved 

 beyond dispute. He mentions many diseases, having a very good grasp of the literature; 

 and admits the following 15 as of clearly-established bacterial origin: The black vein 

 disease of crucifers due to Ps. campestris; the wilt of Solanaceae due to B. solanacearum, 

 the wilt of cucurbits due to Bacillus tracheiphilus; the yellow disease of hyacinths due to 

 Ps. hyacinthi; the bacterial gummosis of sugar-beets due to B. betae; the maize disease 

 due to Ps. stcwarii; pear-blight due to Bacillus amylovorus; lilac-blight due to Ps. syringae; 

 the olive tubercle due to B. oleae; the spot disease of beans due to Ps. phaseoli; potato-rot 

 due to various bacteria (B. solaniperda, B. solanacearum, B. atrosepticus, etc.); carrot-rot 

 due to B. carotovorus; turnip-rot due to Ps. destructans; iris-rot due to Ps. iridis and 

 B. omnivorus: hyacinth-rot due to B. hyacinthi septicus. 



The original matter in this thesis will be discussed under the various diseases. 



In 1903, in the second edition of his Vorlesungen, Fischer repeats many of the inad- 

 missible statements of his earlier edition, but, nevertheless, gives several pages to a review 

 of a few bacterial disease of plants, dealing briefly with the rot of fleshy roots, potato-rot, 

 the black-rot of cabbage, the mosaic disease of tobacco, and tree-cancers. Concerning the 

 latter we have the following : 



Bacteria as the cause of cankers are unknown, for the Bacillus oleae which is said to cause the 

 canker-like swellings of the olive-tree is no more legitimatized by pathological experiment than many 

 other bacteria described as pathogenic for plants. 



It is fitting that these citations should end as they began, with Sorauer's Pflanzen- 

 krankheiten. The second volume of the third edition devotes many pages to the subject 

 of bacterial diseases of plants. This purely didactic review published in 1905, contains 

 the best summary in any general treatise on plant diseases. About 70 bacterial diseases 

 are considered. The statements in it, carefully as the literature has been gone over by Dr. 

 Ivindau, show, however, perhaps as clearly as anything, the great need for a re-examination 

 of the whole subject by some one experimentally familiar with it. 



Most of the conclusions I have cited in this chapter are to be regarded simply as 

 ex cathedra judgments, or to put it somewhat differently they are to be regarded only as 

 so many evidences respecting the ability of the particular writers to reason logically and 

 arrive at sound conclusions from a maze of contradictory statements. In other words 

 they are literary or legal judgments rather than scientific ones. A good judge must have 

 not only a keen, well-balanced mind, but he must also know the case and the law. Very 

 few of the writers I have cited appear to have had any extensive acquaintance with this 

 class of diseases, or with the rules of evidence guiding in pathology, and those who have 

 rendered adverse judgments seem to have had none whatever, i. e., they made few observa- 

 tions and no experiments, or only some irrelevant ones. It is no wonder, therefore, that 

 the insight of some of these writers has been much shrewder than that of others, or that 

 most of them should have mingled fact and fancy in nearly equal portions in what they 



