24 BACTERIA IN RELATION TO PLANT DISEASES. 



In 1882, Prof. T. J. Burrill described a Micrococcus toxicatus as the essential virus of 

 the Poison Ivy (Rhus toxicodendron). It is now believed that the poison of Rhus is not 

 due to a micro-organism but to a chemical substance: A non-volatile oil fPfaff) ; a gluco- 

 side (Syme). 



In 1884, Jorisson ascribed the formation of diastase in the higher plants to the pres- 

 ence of bacteria in the tissues. In the following year, however, Laurent pointed out errors 

 in Jorisson's work. Laurent himself reached the conclusion that there are no bacteria 

 normally present in living plants. 



Galippe (1887) examined the inner tissues of many kinds of vegetables from the vicinity 

 of Paris and found bacteria so constantly present, except in garlic, that the reader is at 

 once led to suspect some serious error in his methods of work. No quantitative tests were 

 made of the number of bacteria per gram of tissue or per cubic centimeter of juice, and it 

 is possible that those which appeared so regularly in the author's tubes are to be ascribed 

 either to the use of wounded or wilted vegetables, to air contaminations occurring at the 

 time the cultures were made, or to imperfectly sterilized media, especially as his results are 

 not in accord with those of Fernbach. 



Galippe first experimented with vegetables grown on a soil supersaturated with sewage- 

 bacteria, i. e., with those grown in the municipal experiment gardens on the plain of 

 Gennevilliers, near Paris. 



The vegetables tested were exposed to the Bunsen flame until the surface was car- 

 bonized. They were cut with a hot, sterile knife. Each surface of the section was then 

 flamed. Finally, by means of a hot sterile knife (heated above ioo C.) "I detached 

 fragments of the vegetable which were put directly into the culture-fluid, choosing the 

 most central parts. I strove as far as possible to remove sources of error." 



His culture-media were: (1) ordinary bouillon; (2) peptonized bouillon with sugar; (3) 

 same, neutralized; (4) saliva peptonized and sugared; (5) same, neutralized; (6) broths 

 from the vegetables experimented upon; (7) same, with peptone and sugar. 



A long series of experiments was instituted, the culture-media being inoculated from 

 carrot, onion, celery, parsnip, turnip, potato, beet, lettuce, salsify, leek, cabbage, Brussels 

 sprouts, Jerusalem artichoke, garlic. All gave positive results except garlic. The juice of 

 the latter is said to sterilize culture-fluids. 



A second series of experiments was made, using vegetables taken from the market- 

 gardens about Paris. Concerning their origin only one thing was ascertained carefully, 

 namely, they did not come from Gennevilliers. These are styled normal vegetables. The 

 author obtained substantially the same results with these vegetables, viz., the clouding of 

 most of his culture-media. 



His general conclusions, therefore, are: (1) the micro-organisms of the soil can pene- 

 trate into the tissues of the vegetables with which they are in contact, the mechanism of 

 this penetration remaining to be elucidated; (2) the number of the micro-organisms con- 

 tained in the vegetables seems to vary with the number in the dung used. 



There is no statement in the paper as to how the culture-media was sterilized ; where 

 the inoculations were made, c. g., whether in a clean room, free from air-currents; nor as 

 to whether check-tubes of the various culture-media were generally held for comparison 

 and remained sterile. All we are told is that some of the many inoculated tubes remained 

 sterile. Concerning these results, as already hinted, conclusions quite different from those 

 of the author might be drawn. 



Fernbach carefully repeated the experiments of Galippe and published a paper on the 

 subject in 1888. He found all of Galippe's conclusions erroneous. In all cases, except 

 that of the tomato, pieces of the interior tissue were removed and thrown into the culture- 

 media. In all, 98 different specimens were examined. Of the 555 inoculations only 35, 

 i. c., 6.3 per cent, developed any growths. This number is considered about the minimum 

 of necessary contaminations, arising from air-currents and other imperfect conditions under 



