1 8 BACTERIA IN RELATION TO PLANT DISEASES. 



plants in general presuppose previous disease due to fungi. They bear the name of rot diseases or 

 hacterioses. Through the transfer of bacteria from diseased to sound plants the sickening of sound 

 plants can be induced. 



In 1 90 1, in his Disease in Plants, under "Exudations and Rotting," Marshall "Ward, 

 then leading English writer on plant pathology, has the following on bacterial diseases: 



In many of these cases bacteria abound in the putrefying mass, and some evidence exists for 

 connecting these microbes causally with the disease in a few of the more thoroughly investigated 

 cases, but in no case has this been sufficiently demonstrated; and considering the ease with which 

 bacteria gain access via wounds caused by insects and fungi, as well as by other agents, the neces- 

 sity for rigid proof must be insisted upon before we can accept such alleged examples of Bacieriosis. 

 * * * Wet-rot of potatoes may be due to various fungi, and, in excess of water, to putrefactive 

 bacteria. * * * -j^j^g principal agent in the destruction of the tissues is Clostridium, an anaerobic 

 bacillus which consumes the cell-walls but leaves the starch intact. * * * The rotting of bulbs, 

 roots, etc., has been much discussed during the last few years in the pages of the Gardeners' Chronicle, 

 Zeitschrift fiir Pflanzenkh., and elsewhere. The principal references to Bacteriosis — the rot in which 

 bacteria are stated to be the primary agent causing these and similar diseases — ^may be found in 

 Massee, Diseases of Plants, pp. 338-342, and more fully in Russell, Bacteria in their Relation to 

 Vegetable Tissue, Baltimore, 1892; and in Migula, Kritische Uebersicht derjenigen Pflanzen- 

 krankheiten, welche angeblich durch Bakterien verursacht werden, Semarang, 1892. 



The most convincing accounts, however, are since that date; see Smith, Pseudomonas campestris, 

 Cent. f. Bakt., B. Ill, 1897, p. 284, and Arthur and BoUey, Bacteriosis of Carnations, Purdue Uni- 

 versity Agr. Expt. Station, 1896, vol. VII, p. 17. Woods has lately shown that this disease is due 

 to Aphides only, the bacteria having nothing to do with the disease primarily, Siigmonose, Bull. 19, 

 U. S. Dept. Agr., 1900; but it is necessary to bear in mind that actual penetration of the cell- walls 

 from without must be proved, as De Bary proved it for germ-tubes of fungi, before the evidence 

 that bacteria are truly parasitic in living plants can be called decisive. This is a difficult matter, 

 but until it is settled we do not know whether these organisms are really parasitic in the sense that 

 Phylophthora is, or merely gain access by other means — I have traced them through dead fungus- 

 hyphse — to the vessels, dead cell-walls, etc. The proof of infection via water pores and vessels is 

 given for one species by Harding, Die Schwarze Faulnis des Kohls, etc.. Cent. f. Bakt., Abt. II., B. 

 VI., 1900, p. 305, with literature. * * * 



On Bacteriosis in Turnips, see Potter, Proc. R. S., 1901, vol. lxvii., p. 442. 



In Conn's Agricultural Bacteriology, published in 1901, 5 pages out of 419 are devoted 

 to bacterial diseases among plants, but some of the specific statements will scarcely pass 

 muster, e. g., those respecting the olive-tubercle. The author's standpoint is sufficiently 

 illustrated by the following citation : 



It has been claimed that there is no likehhood that bacteria can live under such conditions and 

 that bacterial diseases are, therefore, on a priori grounds, improbable or impossible. Even in very 

 recent years this claim has been very vigorously supported, and disputes are still going on in the 

 pages of bacteriological journals, in regard to the question of the existence of bacterial disease in 

 plants. Almost to the very present day, it has been insisted that there is no demonstration that 

 bacteria can produce disease in plants. Although this claim was legitimately urged a few years ago 

 by conservative scientists, it can no longer be held in the light of recent experiments. In the last 

 few years the evidence for such diseases has accumulated rapidly, and to-day the proof of the 

 existence of bacterial plant diseases stands on identically the same basis as the proof of bacterial 

 diseases among animals. 



In Neppi's Itahan translation of Kirchner's book, pubhshed at Turin in 1901, various 

 bacterial diseases are mentioned with the organisms said to be their cause. These are: 

 The red disease of wheat kernels (Af. tritici), internal rotting of corn-stalks and sorghum 

 {B. termo), celery rot (5. a^M),Bolley's potato scab, Kellerman's sorghum disease (S.5org/ii), 

 gangrene of potato stems {B. caulivorus), brown-rot of potato {B. solanacearum) , beet 

 disease {B. betae), hemp disease (B. cubonianus), wilt of cucumbers, etc. (B. tracheiphilus) , 

 disease of vine stems {B. vitivorus), rot of grape bunches, soft rot of potatoes, onions', 

 etc. {Clostridium butyricum), tumors on peach branches described by Cavara. 



Plates ix-xiv in Delacroix's Atlas (1901) are devoted to bacterial diseases of plants, 

 viz., to tubercle of the olive and of the Aleppo pine, gummosis of vine, red disease of wheat' 



