169 



STUDIES IN BACTERIOSIS. VI 



BACILLUS CAROTOVOEUS AS THE CAUSE 

 OF SOFT-ROT IN CULTIVATED VIOLETS 



By MARGARET S. LACEY. 



{From the Department of Plant Physiology and Pathology, 

 Imperial College of Science and Technology, London.) 



A DISEASE of some considerable importance occurred in the early part 

 of 1921 at the Hayden Violet Grounds, Stourpaine. When received, the 

 plants were in an advanced state of decomposition; the whole interior 

 of the stem was reduced to a soft white mush, and the rot was spreading 

 up the petioles; several of the leaves had already fallen off owing to 

 decay at the base of the petioles, and others were dying from the same 

 cause. 



Owing to the advanced state of decay considerable difficulty was 

 experienced in isolating the causal organism, but eventually a pure 

 culture of a white organism which produced vigorous rotting of vegetables 

 was obtained. 



Inoculation Experiments upon Cultivated Violets. 



Underground stems, "runners," and the apices of stems were used 

 in these experiments. In all cases, rotting of the tissues round the point 

 of inoculation was obtained. In the case of stem infections the rottino- 

 proceeded rapidly, after 48 hours the petioles had been attacked and 

 the leaves were dying, after a week a rotted mass from which the leaves 

 had fallen was all that remained. In all cases the controls remained 

 healthy. The organism also produced white rot of carrots, turnips, 

 potatoes and onions. 



Identification of the Causal OrganiSxM. 



The organism was carefully compared with the laboratory culture of 

 Bacillus carotovorus (strain obtained from Prof. L. R. Jones in 1911). 

 The latter had an average length of 1-2/a and varied from 1-1-6/z, 

 whereas the violet strain had an average length of 3/x and varied from 

 1-4 /x with occasional larger cells up to 10 fi. Apart from this difference 



