WILT-DISEASES OF TOBACCO. 



245 



In another series of inoculations, 99 out of 103 plants contracted the disease, 13 checks remaining 

 sound. These were as shown in table 27. 



TABLE 27. Result of Further Inoculations by Honing. 



*Ag. = Agcra turn ; T = Tobacco. The small letters denote plant selected. In 7 cases the strain was re-inoculated 

 into tobacco and rcisolated before using, the sub-figures denoting the particular plant from which reisolated. 



Time alone can tell whether cultivation, rotation, disinfection, or selection of less susceptible 

 races will prove most serviceable in combating this disease. 



Some planters have said that the slime-bacteria would not attack plants under ideal food condi- 

 tions, but this can not be admitted. Inoculated potato plants (16 in number) from two sources 

 contracted the disease within a week, although they were obtaining their food directly from the mother 

 tuber. It is likely that any plant of susceptible sort, variety, or race will be attacked, no matter what 

 the food conditions. 



It is impractical to prove absence of the slime-bacteria from the soil by the ordinary plate method, 

 but cuttings of tobacco plants may be used. In an experiment in which soil-water from pots, which 

 had been infected about 6 weeks before, was diluted with tap water in 5 dishes and 2 cuttings put into 

 each, 9 of the 10 plants contracted the disease. 



In two tests made in the same way with suspected soil from two fields, each with 9 cuttings, 7 

 were positive for soil of one field, 2 only for that of the other. If such tests, therefore, are made, a 

 considerable number of cuttings should be used. Because the soft tobacco stems rot easily, Honing 

 substituted the harder stems of Ageratum and Pouzolzia successfully, but then had to wait longer. 



Although unquestionably the slime-bacteria are killed off in the soil by other organisms (other- 

 wise there would soon be nothing else in the soil), nevertheless the fact remains that they may persist 

 in the soil for years. 



The continuation of the experiments with chloride of lime and potassium permanganate yielded 

 nothing very hopeful, as may be seen from the following experiment (table 28) on 1,392 plants in 5 

 similar plots: 



TABLE 28. Effect of Soil Treatment on Sumatran Tobacco-Disease. 



This was the worst field. None, however, were very hopeful. The best plot gave 1 1 per cent 

 more sound plants than the control. 



The remainder of this paper is taken up with discussion of morphological and cultural char- 

 acters of the slime-bacteria, which are here omitted because treated more fully in one of the following 

 papers. 



(2) THE CAUSE OF THE SLIME-DISEASE AND ATTEMPTS TO COMBAT IT HI. 



In the year 191 1 , up to April, Honing received of tobacco seedlings diseased by the slime-bacteria, 

 44 samples from 24 plantations. 



Many of these fields were visited and frequently the disease was found showing in the seedlings 

 so slightly that they would have been selected for planting, especially those infected in the leaves. 

 On a plantation where the leaves of the seedlings were supposed to have been injured by guano or 

 Schweinfurth green, the actual cause of the injury proved to be this bacterium, and all stages were 



