300 A Bacterial Disease of Taniip (lirassicii Nai>iis) 



stained easily with tlie aiiilin dyes, particularly carbol-fuchsin, followed 

 by differentiation in alcohol, showing the bacteria to advantage. Another 

 method was to stain for 12 hours in HofFniann-blue saturated with 

 picric acid, and after washing in 50 per cent, alcohol, to immerse for 

 three minutes in carbol-fuchsin. This showed the tissues blue and the 

 bacteria red, but the staining was not always uniform and hence the 

 method was unreHable. After repeated attempts with various dyes 

 satisfactory results were obtained by the use of Heidenhain's iron-alum- 

 liaeraatoxylin followed by eosin in dove-oil. Tliis showed the bacteria 

 black and the cell- walls light red. 



When the slides were exainincd under the Iow-jkiwci- of the micro- 

 scope, the bacteria were seen to be apparently e.xclusively confined to 

 the intercellular system of the medulla, and the disintegration of the 

 tissues to be brought about by the dissolution of the middle lamella. 

 Some cells in the same region were seen to be densely filled with bacteria, 

 relatively few or none being present in contiguous cells, thus repeating 

 the features already observed in the examination of the diseased pulp. 

 Some of the xylem elements also seemed to be occupied by bacteria. 

 The microscopic examination of microtomed sections derived from 

 artificially inoculated roots revealed an exactly similar invasion of the 

 tissues to that seen in the field material. Tlie bacteria abounded in 

 the intercellular spares of the inner tissues; occasional parenchyma 

 cells were densely filled with bacteria, whereas the peripheral tissues were 

 intact. 



Separation ok thk Bacteria from their Products. 



The separation of the by-|)roducts from the bacteria was then 

 attempted. A two-litre flask containing a little water and sterilized by 

 intermittent steaming was half filled with sterile blocks of turnip, a 

 diseased block from a test-tube dropped in, and the flask quickly plugged. 

 After four days' incubation at 20° the whole of the contents had been 

 reduced to a pulpy putrid mass with a highly offensive odour. This was 

 pressed through a piece of coarse linen and the turbid filtrate passed 

 through filter-paper. The grey-coloured liquid was then divided into 

 two portions — one portion was passed through a Berkefeld filter which 

 had been sterihzed for several hours in the hot-air oven and allowed to 

 cool. The clear pale yellow filtrate was poured into a number of small, 

 sterile test-tubes and corked with sterilized rubber bungs. To the other 

 portion was added four times its bulk of 80 per cent, alcohol. After 

 24 hours a heavy flocculent precipitate had been formed. The super- 



