266 BACTERIA IN RELATION TO PLANT DISEASES. 



This paper was discussed by various botanists and Woronin suggested that, owing to 

 the serious nature of these diseases, a commission be appointed to study them further. 

 Query: Was this commission appointed and did it publish any report? 



THE ITALIAN DISEASE. 



From a line or two in Comes's "Crittogamia agraria," page 515, it would appear that 

 he has seen in Italy a bacterial rot of tobacco. This he ascribes to his Bacterium gummis. 



Comes also reports a bacterial rot of seedlings, but this was also associated with a 

 fungus and with eel-worms. 



THE FRENCH DISEASE. 



In 1906 Delacroix described several so-called bacterial wilt-diseases of tobacco. His 

 "canker," "collar-rot," and "pith-rot" seem to belong here, or at least may be placed here 

 tentatively. He has, however, ascribed these three diseases to as many species, two of 

 which are green fluorescent schizomycetes. The "canker," which has done much damage 

 in parts of France, particularly in Meurthe-et-Moselle and in Haute-Savoie, is said to be 

 due to Bacillus aruginosus Delacroix. The collar-rot is ascribed to Bacillus tabacivorus 

 Delacroix. The pith-rot is attributed to Bacillus putrifaciens putridus Fliigge. These are 

 described with about the same degree of completeness as his Bacillus solanincola. In 

 particular the account of his isolation and infection experiments leaves much to be desired ; 

 one also feels inclined to suspect that the descriptions of behavior on media may have been 

 drawn from mixed growths. I could not come to any definite conclusion from a hasty 

 examination of his alcoholic material made in Paris in 1913, but a careful examination 

 since made of stained sections of paraffin embedded material (10 sets, two sources) leads 

 to the conclusion that no bacteria are present in the samples examined. 



These three organisms are said to have the following characteristics: 



(i) Bacillus (zruginosus. The bacteria are elongated cylindric with rounded ends, generally 

 occurring isolated or as diplococci, 0.75 to i .oX 2 to 3/1 (his figure represents a somewhat larger organ- 

 ism). It has no cilia, spores, capsules, or zoogloeae, and does not stain by Gram's method. It grows 

 well in culture-media: nutrient agar, nutrient gelatin; aerobic; forms on bouillon a thin, whitish, 

 fugacious pellicle, quite adherent to the walls of the tube; the bouillon clouds rapidly and shows a 

 green fluorescence inclining to olivaceous, the precipitate being first white, then pale yellowish- 

 cream, and finally slightly grayish. After a time the liquid clears, loses its green color, and gradually 

 becomes fawn-brown, old cultures having the smell of incompletely burned tobacco; this odor, how- 

 ever, is not always produced, even in veal-bouillon ; gelatin is not liquified, but after some days it 

 acquires a green fluorescence which lasts longer than in bouillon. The isolated colonies are discoidal, 

 2 to 3 mm. in diameter, smooth, shining on the surface, pale yellow, becoming darker with age ; the 

 colonies often fuse. On agar there is a green fluorescence ; the surface of the colonies is brilliant, but 

 when they become confluent the surface is duller and mammelonate, with the border flattened out 

 more than that of the single colony, or than the fusions on gelatin ; the margin also extends as the cul- 

 ture ages; they are a little paler than on gelatin, and sometimes a little greenish; on potato the colonies 

 are golden-yellow, slightly granular, quite brilliant, forming by confluence a creamy, opaque mass, 

 which sinks down and becomes brown with age. These bacteria are often mixed with others in the 

 plant, and cultures should be made, for this reason, from recent infections. Inoculation experiments 

 by means of a needle succeeded in the proportion of 3 to 8 ; inoculations in the middle of August, made 

 by placing a drop of the culture on the freshly cut stem (top of the plant) gave i out of 3 positive. 

 Signs were visible in a week, but at the end of a month there was only a slight chancre; wounds are 

 necessary. Cultures of the second generation gave no result when inoculated ; direct infections gen- 

 erally failed. The chancre frequently attacks the Paraguay, more rarely the Auriac. It has not 

 been seen on the Green Dragon. Nicotiana rustica did not contract the disease from inoculations. 



Bacillus tabacivorus. The elements are isolated, cylindrical, with rounded ends; spores, cilia, 

 capsules, and zoogloeae are absent; rods vary in size from 0.4 to 0.6X0.75 to 1.501*. Agar, gelatin, 

 and bouillon are not stained; the organism is aerobic; in bouillon the liquid becomes opaque (louche), 

 with a slight pellicle which adheres to the walls of the tube. There is a scanty, whitish precipitate. 



On gelatin the colonies are opaque, 1.5 mm. in diameter, brilliant metallic-iridescent, with a 

 duller, slightly raised central portion ; they are flat, dirty white, with a slightly irregular contour and 

 a surface radially striate; the gelatin is not liquefied. On agar the colonies are noticeably duller and 



