THE CELERY-ROT BACILLUS^. 



By H. WORMALD, A.R.C.Sc, M.Sc. (Loud.). 

 (Mycological Department, South-Eastern Agricultural College, Wye.) 



In previous papers (46, 47) it has been shown that the celery plant 

 is susceptible to bacterial attack, producing in the affected tissues a 

 brown soft-rot which in serious cases may be so pronounced that on 

 lifting the crop a high percentage of the plants is found to be quite 

 worthless^. From such rotting material a Bacillus was isolated and 

 this, when introduced into the tissues of healthy celery plants, readily 

 induced in the inoculated organs a rapid decay similar to that observed 

 on naturally infected plants. An account of inoculation experiments 

 performed on celery plants with a description of the behaviour of the 

 organism when grown on artificially prepared media has already 

 appeared, and further observations concerning its pathogenesis in 

 living plants and its development on certain culture media are recorded 

 in the present paper. 



I. Pathogenesis of the Celery-Rot Organism. 



Inoculation of Celery Plants. Numerous inoculations from pure 

 cultures have been performed on celery plants, the usual procedure 

 being as follows: — A streak culture of the bacillus is made on celery- 

 extract agar^ and incubated at 26° C. After 24 hours there is a 

 creamy-white growth along the streak and a little of this is transferred 

 by means of a flamed platinum loop to the upper end of a petiole of 



1 The present paper is an abridgment of a Thesis (presented March 1, 1916) approved 

 for the Degree of Master of Science in the University of London. 



2 See Table in Jour. South-Easlern Agric. Coll. No. xxii, 1913, p. 4()1. or Reprint 

 from same, p. 75. 



* The preparation of this culture medium is described in Jour. Agric. Set. Vol. vi. 

 footnote, p. 212. 



