14 BACTERIA IN RELATION TO PLANT DISEASES. 



Hallier (1895) asserts the existence of bacterial rots but does not attempt to make a 

 list of them. They follow fungi or act independently, but in all cases, Hallier would have 

 us believe that the bacteria themselves have developed out of the plastids (protoplasmic 

 granules) of the fungi. 



The second edition of Frank's book on plant diseases, published in 1896, contains 1,213 

 pages (3 volumes), 13 only of which are devoted to bacterial diseases of plants. There is 

 a good deal of internal evidence (careless proof-reading, etc.) going to show that this book 

 was thrown together very hastily. The arguments in the chapter on bacteria in particular 

 are vague and inconclusive. This is made sufficiently plain by the following paragraph : 



On the contrary, in the plant-world the bacteria have a very subordinate place in the production 

 of diseases. The striking bacterial action on the plant is consequently not of a pathological char- 

 acter, but a profitable symbiosis, to wit, that in the root-tubercles of the Leguminosae. Where one 

 has perhaps the right to speak, in connection with plant diseases, of bacteria as causes of disease 

 is in a number of rot phenomena of certain underground plant parts. Sorauer proposes, under the 

 hypothetical assumption that these diseases are caused by bacteria, to designate the same by the 

 common name rot or bacleriosis. But, in truth, we have here to do, for the most part, with very 

 ordinary rot phenomena which represent the regular end stage of other diseases, in which, demon- 

 strably, the genuine higher fungi, or also other external factors, are the true primary disease- 

 producer, and decay-bacteria appear only secondarily in the tissue, dead in consequence of the 

 disease, and, powerfully hasten the progress of the destruction of the diseased plant parts on account 

 of the decay which they set up; not rarely, also, are associated with other decay-loving fungi, 

 especially moulds. But because, in isolated cases, it has been possible to produce similar decay 

 phenomena by inoculating sound plant parts with bacteria taken from rotting plants, a number of 

 pathologists insist on viewing these bacteria also as primary causes of disease. Moreover, some 

 cases of hypertrophy, that is of true gall formation, are known in which bacteria are said to be the 

 cause. In the following pages we register all that is known of an authoritative character. From 

 this it will be seen that a satisfactory proof for the acceptance of pathogenic bacteria has not been 

 furnished, and that many times people have sought to help out with a supposition of bacteria as a 

 cause, in diseases which may be brought about through another cause, or the cause of which is not 

 easy to discover, or which also have not been sufficiently investigated by the observer in question. 



Then follows a discussion of the wet-rot of potato, in which there is no mention of the 

 then most important paper on the subject, viz., Kramer's; the white and yellow rot of the 

 hyacinth, in which the two diseases are confused, in which Wakker's five papers are con- 

 densed into four lines, and in which there is no mention of Heinz's paper. The most of the 

 two pages on this disease is devoted to Sorauer and the digest concludes with the state- 

 ment that "there is at least yet no proof of a pathogenic bacterial action." The rot of 

 onions is discussed briefly from data published by Sorauer. Bolley's work on potato scab 

 and beet scab is then considered, following which are notes on various other diseases: 

 olive-tubercle, Aleppo pine gall, rose-red disease of wheat grains, pear-blight, etc. Under 

 bacteriosis of the sugar-beet there is no mention of Kramer's paper or of Sorauer's second 

 note published in 1892. 



There is evidence throughout that many of the original papers were never seen or, 

 if seen, were not read. 



The last edition of Fliigge's large general work on microorganisms (1896) contains 1,385 

 pages, of which three and one-half are devoted to bacterial diseases of plants, following 

 Migula and I/udwig (vol. n, p. 418; vol. n, pp. 308 and 328). 



Most general treatises on bacteriology do not discuss this subject at all and even so 

 extensive an annual compendium of bacteriology as Baumgarten's Jahresbericht omits all 

 mention of bacterial diseases of plants, although the title is inclusive. 



In the first volume of his System (1897) Migula devotes 12 pages out of 376 to this 

 subject, going over the literature in the same careful way as in his earlier publication. Out 

 of 29 diseases mentioned, the 8 following are considered to be of proved bacterial origin: 

 Sorghum-blight, pear-blight, Cobb's gum disease of sugar-cane, olive-tubercle, Kramer's 

 wet-rot of potato, Heinz's rot of hyacinths, Arthur and Bolley's spot disease of carnation, 

 and Smith's wilt of cucurbits. 



