H. WORMALD 221 



fissures 0-5 cm. to 3 cm. in length, these cracks were bordered by a 

 fringe of desiccated tissue and there was no evidence of a soft rot or 

 even of further splitting to the end of the experiment. 



These results are interesting from the fact that Erwin F. Smith 

 records^ failure to obtain positive infection results from experiments 

 in which Bacillus carotovorus was inoculated into green potato shoots. 



The organism appears to be unable to attack uninjured living 

 organs. In one experiment young plants of celery, parsley and carrot, 

 some of which were quite sound so far as could be observed and free 

 from aphides, others bearing a considerable number of aphides, were 

 sprayed (using an atomizer) wdth an emulsion made by placing the 

 product of a streak culture, 24 hours old, in water which had previously 

 been sterilized. The plants were then kept in a glass case to maintain 

 a damp atmosphere, but no rot set in on any of the plants, though, 

 as shown earlier in this paper, young celery plants, the laminae of which 

 had been punctured previously to similar treatment, became infected. 

 In another experiment a young turnip plant growing in a pot was 

 watered and placed under a bell-jar. On the following day the leaves 

 were fringed with drops of water which had issued from the water 

 pores around the margins of the laminae. Bacilli were transferred 

 to a number of these drops by removing, with a platinum loop, droplets 

 of the turbid liquid (water of condensation containing the bacteria) 

 at the base of a streak culture and bringing these droplets in contact 

 with the drops of water on one of the leaves, care being taken not to 

 touch the leaf itself thus avoiding a rupture of the epidermal cells. 

 No signs of rot appeared so evidently the bacillus was unable to attack 

 through the water-pores. In this way the celery-rot bacillus differs 

 from the "Black-Rot" organism {Pseudomonas cam'pestris), for the 

 latter readily produces infection through water-pores as has been 

 proved by Erwin F. Smith (37)2. 



Middle lamella destroyed. If a little of the bacteria-containing 

 pulp from a diseased celery plant be placed in a tube of water and shaken, 

 the cells readily separate from one another, and when a drop of the 

 resulting turbid liquid is examined microscopically numerous isolated 

 cells are to be found, indicating that the organism attacks primarily 

 the middle lamella. 



It has been shown by Potter (28, 29), Spieckermann (40), Harrison (12), 

 van Hall (9) and Jones (17, 18), that the soft- rot organisms produce an 



^ Bacteria in Relation to Plant Diseases, Vol. ii, p. 96. 



^ See also Bacteiia in Relation to Pkini Diseases, Vol. ii. pp. 54-G4. 



15—2 



