214 BACTERIA IN RELATION TO PLANT DISEASES. 



THE CEYLON DISEASE. 



In 1909, Petch reported very briefly on a wilt disease of tomato plants occurring in Cey- 

 lon, during a period of wet weather, and first visible when the plants were in bearing. 



The wilted leaves decayed and fell off, and finally the stems decayed also. There is very little 

 evidence of disease in the stem when the leaves begin to droop,- but if it is cut across near the base the 

 woody part immediately round the pith is found to be brownish, and minute white or yellowish drops 

 of liquid ooze out from this region. These drops consist of enormous numbers of bacteria, and if sec- 

 tions of the stem are examined under a microscope, they are found to issue from the vessels of the 

 wood which are completely filled by them. * * * 



The bacterium is, as far as can be ascertained without elaborate bacteriological investigation, 

 Bacillus solanacearum. 



THE AFRICAN DISEASE. 



The writer's knowledge of the African potato-disease here referred to was obtained from 

 a conversation with Mr. George Milton Odium, a student of scientific agriculture, who for 

 some time had charge of plantations for English capitalists at Umtali, in Rhodesia, where he 

 saw the disease. He described it to me as a bacterial rot, beginning as a black stain in the 

 vascular system; the foliage wilts, the stems shrivel and blacken, or have black stripes in 

 them, and the tubers decay. He has known whole fields to be destroyed quite suddenly. 

 The microscope always shows great numbers of bacteria in the diseased plants. In his 

 opinion the disease is the same as that described by the writer. 



THE RUSSIAN DISEASE. 



In 1899, Iwanoff reported the occurrence in 1898, in all of the fields for a distance of 26 

 miles around St. Petersburg, of a very destructive bacterial disease of potatoes closely resem- 

 bling that due to Smith's Bacillus solanacearum, ii not the same. The organism present in the 

 stems in the earliest stage of the disease is described as a "small, short, oval-cylindric, 

 actively motile rod of medium size (in general rather variable) 1.5 Xo.5^. " 



Two organisms isolated from the diseased stems in pure culture were not infectious, but 

 direct infections were successful. 



The tissues were browned, the bacteria passed up and down the stem from the point of 

 inoculation by way of the vessels, the pith was badly disorganized, the starch was not 

 attacked, young plants were killed much sooner than old woody ones, the juice of diseased 

 plants was alkaline, and in the pith and the bark parenchyma there was an increased produc- 

 tion of calcium oxalate. The tubers were small and few, but were not observed to be dis- 

 eased. The disease spread with great rapidity. A field which contained only scattering 

 cases on August 8, showed all plants diseased on August 15, the only green things in the field, 

 and in many similar fields, being weeds. Possibly this should be referred to B. phytophthorus. 



THE FRENCH DISEASE. 



In 1901, in two publications, Delacroix stated that Smith's disease of the potato was 

 prevalent in France. I translate as follows: 



The bacteria are found far up in the stem and in parts apparently still living. They are espe- 

 cially numerous in the vessels. This bacterium seems to me not different from the Bacillus sola- 



irum of Krwin F. Smith. Its cultural characters are the same; the signs of the disease observed 

 in the United States on the potato, tomato, and egg-plant are exactly those I have myself seen. 



Afterward Delacroix attributed the disease to a green fluorescent bacillus, B. solanincola 

 I klacT.. which is different from Bad. solanacearum, but non-pathogenic in my hands. 



Here again, it is uncertain whether we have to do vfithBacillus phytophthorus, Bacto ium 

 5 ,' macearum, or some third organism. The writer obtained a culture of B. solanincola from 

 Prof. L- R. Jones, to whom it was given in Paris by Delacroix, but either it never possessed 



