H. WORMALD 217 



the plant to be inoculated; a single prick is then made with a sterile 

 steel needle passing through the mass of bacteria and piercing the leaf- 

 stalk. The inoculations have been made on young plants growing 

 in pots and on older plants brought from the garden and placed with 

 their roots in water. When the inoculated petioles contain a relatively- 

 large proportion of turgid parenchymatous cells, as in the case of leaves 

 of rapidly growing young plants or the blanched inner leaves of the 

 older ones, the rot makes rapid progress and the infected leaf usually 

 collapses from above the point of inoculation in from 24 to 48 hours 

 b}^ the conversion of the tissues in the neighbourhood of the wound 

 into a soft translucent brown pulp. Older leaves that have attained 

 their maximum size are less susceptible and in these the inoculations 

 frequently gave negative results ; young plants that have been grown 

 under comparatively dry conditions are also resistant. Control 

 leaves pricked with sterile needles invariably gave negative results. 



Young celery plants were also successfully inoculated by puncturing 

 the laminae of the leaves which were then sprayed with bacteria taken 

 from a pure culture and diffused in sterilized distilled water, the result- 

 ant bacterial suspension being applied to the leaves by means of an 

 atomizer. Translucent water-soaked spots up to 1-2 cm. in diameter 

 appeared within 48 hours ; these were irregular in outline, being more 

 or less angular and limited by. the larger veins. In some cases the 

 leaflets were gradually destroyed, in others- the veins prevented the 

 extension of the rot. 



In order to ascertain what crops should not be grown on soil where 

 diseased celery has been, inoculations were made on plants other than 

 celery with results as described below. 



Action of the Organism on Slices cut from healthy Roots and Tubers. 



The root or tuber was soaked for two minutes in 0-1 % aqueous 

 solution of mercuric chloride, then dropped into sterilized tap-water 

 and finally washed over with sterilized distilled water. The slices 

 were cut with a razor that was kept in 94 % alcohol until required, 

 when the alcohol was burnt off by passing the razor through a bunsen 

 flame. As each slice was cut it was dropped into a sterile petri dish 

 and cut into halves with a sterile scalpel. One half of each slice was 

 then inoculated from a pure culture, the other half being kept as 

 control. 



The organism readily produced a soft rot on slices of radish, potato, 

 carrot, artichoke, turnip and swede. On slices of parsnip and mangel- 



