— 60 — 



economic losses to farmers and vegetable growers, and hence has attracted the 

 attention of numerous investigators to the disease and the organisms producing it. 



As a resume of the literature has been recently published it seems unneces- 

 sary to give any extensive citations. Suffice it to say that AI. C. Potter^, L. R. 

 Jones^, A. Spieckermann^, C. J. J. Van Hall^, F. C. Harrison^, H. A. Harding 

 and W. J. Alorse^, and F. C. Stewart'^ have described with considerable detail the 

 action of various organisms associated with the soft rots of some of the fleshy 

 vegetables. From the practical standpoint it is sufficient for the grower to under- 

 stand that the disease is caused by a bacterial micro-organism, but from the 

 point of view of the biologist there is considerable interest in defining as closely 

 as may be the relationship of the various organisms isolated and described by 

 investigators who have worked on the disease as it occurred in the field and on 

 the various vegetables attacked. 



As a rule, organisms associated with a well defined disease are recognized 

 with a certain degree of ease, but in the case of the 'soft rot' organisms there 

 seems to be no end to the making of species and varieties, and lest we should be 

 accused of the itch of species making, let us state that the present study was 

 undertaken in order to attempt to find out some facts in connection with the re- 

 lationship of these bacteria with a view of establishing a type, and, the proof of 

 the pathogenic nature of the organism in turnips. 



Harding and Alorse^ have attempted to minimise the number of species by 

 bringing these organisms into a few main groups and by describing their cultures 

 by a plus or minus reaction in certain media, and using decimal numbers for the 

 description of each combination. This system, however, ignores the relation of 

 the organism to its host plant, and obscures the natural phylogenetic relationship 

 of bacteria types, nevertheless such an effort is of great use in routine description, 

 and for arranging and cataloguing cultures. 



In the present study we have w-orked out in detail the pathogenicity of an 

 organism belonging to the 'soft rot' type, which was the cause of a rotting disease 

 in turnips, and have described its morphological and cultural features in detail. 

 Several important peculiarities have been noticed, and as far as possible these 

 have been photographed. 



Our attention was first directed to this disease by Mr. Paul A. Boving. B.A., 

 B.S.A., assistant in the cereal husbandry department of IMacdonald College, and 

 in charge of all the root experiments. Mr. Boving has contributed the field notes 

 of the disease, and has given a number of excellent photographs of the naturally 

 occurring disease, one of which. Fig. 12, is reproduced. 



Field Notes on the Disease. 



The disease was observed during the first week of September, 1912. and the 

 outbreak continued until the end of October, when all roots were pulled and the 

 diseased ones thrown aside. The percentage of diseased plants is shown in the 

 following table : — 



Per cent, diseased plants in turnips of different classes during 1912 : 



6 varieties globe-shaped, white fleshed 12.0% 



4 " long " " " 8.5% 



4 " globe " yellow " 13.7% 



7 " long " " " 5.% 



Average 5.9% 



