226 



BACTERIA IN RELATION TO PLANT DISEASES. 



Once also, Honing has seen, in a slime-inoculated culture on a slice of a tobacco stem, a yeast 

 corresponding to van Breda de Haan's yeast. 



No spores were observed in old cultures of the parasite, but the latter is soon followed by sapro- 

 phytes. 



In the decaying stems five or six kinds of bacteria occur, as may be made out readily, and no 

 doubt careful cultures would show others. The author had not determined the cultural characters 

 of the parasite. 



Dr. Honing says the preceding contains nothing especially new, but is confirmatory or 

 explanatory of the observations of van Breda de Haan, Hunger, Uyeda, Smith, and Jensen. 



Extremely interesting, however, and quite new are his observations that the same or a 

 similar disease occurs on many tobacco fields in wild plants, among these several composites. 

 These plants are: Pouzolzia (a kind of nettle), Ageratum conyzoides, Physalis angulata, 

 Spilanthes acmella, and Pluchea indica. Once the disease was found in Pluchea growing 

 on lalang land which had not been in tobacco for 7 years. The relatively small percentage 

 of disease in the weeds (0.5 to i per cent or less) does not necessarily show them to be less 

 susceptible than the tobacco. It may be only that they are less subject because their root- 

 system is less broken than that of the transplanted tobacco. 



Also from two young diseased Mucuna plants a bacterium was isolated which could 

 not be distinguished from that of the slime-disease. 



Cultures were made from Pouzolzia and from Ageratum and tried on tobacco, June 18. 

 The results on June 29 showed many more cases in three of the inoculated rows than in 

 the controls. 



Counting two of the inoculated groups with the checks, because, as was afterwards 

 discovered, they were inoculated with cultures containing a spore-bearing form clearly not 

 Bad. solanacearum, we have the results given in table 24. 



TABLE 24. Honing' s Results with Pouzolzia and Ageratum. 



P= Pouzolzia. 



A= Ageratum. 



The large number of cases that finally appeared in plats i and 2 are explained as due 

 to the fact that they were worthless rejected plants used as checks only because no others 

 were available. It will be seen that every one of the plants inoculated with the pure 

 cultures by injection contracted the disease and also nearly all of those in which only the 

 ground under the plant was infected. 



The best results in treatment of the soil were with chloride of lime and potassium 

 permanganate. Copper sulphate proved very injurious. Further experiments must be 

 made to determine what doses of the lime and permanganate must be used to disinfect the 

 soil, also whether all the soil of a field must be disinfected or only that under the plant, 

 whether the quality of the tobacco will be injured, and finally, whether rain must be awaited 

 before planting. 



In some cases Honing used 2 to 2.5 grams chloride of lime (Chloorkalk) in i to 2 liters 

 of water for the soil under each plant and the same of potassium permanganate. In other 

 cases he used as high as 6 grams of the chloride of lime per plant, with excellent success 



