86 MASS. EXPERIMENT STATION BULLETIN 175. 



Bacteria and the Mosaic Disease. 



Among the many theories advanced regarding the cause of the mosaic 

 the chief one for some time, particularly among the earlier investigators, 

 was that of bacterial infection either through the agency of infected soil 

 or otherwise. Mayer, ^ in his rather extended study of the disease, came 

 to the conclusion that it was caused by bacteria, but was unable to isolate 

 the organism. Prilleux and Delacroix ^ claimed to have found an organism 

 associated with the mosaicked leaves, but their descriptions leave one in 

 doubt as to whether they were working with the true mosaic disease or 

 not. It is very probable that they were dealing with another disease 

 which occurs in France, but which is somewhat different from the mosaic 

 disease. The next important work on the bacteria supposedly connected 

 with this disease was done by Iwanowski. ^ He isolated several organisms 

 from the juice of diseased leaves, and by reinoculation was able to cause 

 infection, but only in a very small number of instances. This he explains 

 by a probable attenuation of the organism when grown on artificial media. 

 Hunger,* in a very critical review of the bacterial theory, stated that he 

 was unable in any way to substantiate the findings of Iwanowski, and 

 that although he observed certain bodies in the cells, he was not able to 

 classify them as either bacteria or plasmodia, as they disappeared after 

 heating with phenol chloral hydrate, while the rest of the cell contents 

 were unaffected. More recently Allard^ has advanced the opinion as 

 a result of his investigations that the disease is parasitic in nature but 

 does not attempt to discuss the character of the parasite, and apparently 

 has made little attempt to demonstrate anatomically the presence or 

 absence of bacteria. Hunger's work is probably the most satisfactory of 

 its kind along this line. 



The writer has made examinations of diseased plants, sectioning leaves, 

 stems and even the roots, but has never been able satisfactorily to 

 demonstrate the presence of bacteria in the tissues. In this work a 

 variety of stains were used, chief of which, however, were Ziehl's carbol 

 fuchsin and Heidenhain's iron hsemotoxylin. 



It is to be noted in this connection that all investigators have apparently 

 confined their studies to the leaves or part of the plant in which the 

 disease showed itself, and very few attempts, if any, have been made to 

 study the question of the possible presence of bacteria in tissue far removed 

 from the diseased portions. In view of the fact that the juice from all 



' Mayer, A.: Over de in Nederland dikwijk voorkomende Mozaikziekte der Tabak. Land. 

 Tijdschr. (1885). 



» Prilleux, E. E. and Delacroix, G.: Maladies bacillaires de divers v6g6taux. Ck)mpt. Rend. 

 Acad. Sci. Paris, 118: 668-671 (1894). 



» Iwanowski, D.: Uber die Mosaikkrankheit der Tabakspflanze, Zeit. f. Pflanzenkrank, 13: 

 1-41. pi. 1-3 (1903). 



* Hunger, F. W. T.: Untersuchungen und Betrachtungen uber die Mosaikkrankheit der 

 Tabakspflanze. Zeit. f. Pflanzenkrank, 15: 257-311 (1905). 



' AUard, H. A.: Mosaic Disease of Tobacco. U. S. D. A., Bur. Plant Ind. Bui. No. 40 (1914). 



