Studies on the Fire-Blight Organism, Bacillus amylovorus 17 



for the wilting of the twigs. In an attempt to determine this point, 

 some juice from blighted fruit that had been heated to 49° C. for 

 ten minutes was dialyzed through parchment membranes by placing the 

 juice inside the cells and distilled water on the outside. After twenty- 

 tour hours, the cut ends of twigs were placed in the dialyzate inside the 

 cells and in the diffusate on the outside. The twigs in the juice wilted 

 as before, but those in the diffusate remained turgid. 



The question of adsorption by the parchment membrane entered 

 into consideration and collodion membranes were constructed, 50- 

 to 100-cubic-centimeter beakers being used as forms. By duplicating 

 the arrangement of the parchment membranes and permitting the solu- 

 tions to dialyze for twenty-four hours, it was found that twigs placed 

 in the diffusate outside the collodion cells wilted as rapidly as did twigs 

 placed in the dialyzate inside the cells (Plate II, 1). 



Similar results were obtained if untreated juice from blighted pears 

 was used inside the collodion cells. Cultures made from the water on 

 tli-' outside of the cells failed to reveal the presence of any viable 

 fire-blight bacteria. Likewise, the diffusate contained no undissolved 

 organic matter capable of clogging the vessels of the apple shoots. 



As previously stated, juice from blighted fruit that had not been 

 heated nor treated with germicides was dialyzed. This would invalidate 

 the argument that heating produced toxic substances by the disinte- 

 gration of organic compounds. To check further on this point and to 

 ascertain whether freezing would kill fire-blight bacteria, a quantity of 

 juice from blighted pears was frozen to -183° C. for ten minutes. 

 After thawing at 3° C. and dialyzing through collodion, this juice pro- 

 duced results similar to those with untreated juice from blighted fruit. 



In Plate II, 2, are shown apple shoots after they had been inserted 

 for two and one-half hours in (a) juice from blighted pears (at left), 

 (b) juice from healthy green pears (in middle), and (c) distilled water 

 (at right). To all solutions 1 per cent of toluol had previously been 

 added. 



After apple snoots had been inserted in juice from blighted fruit or 

 in the diffusate of such juice for twenty-four to thirty-six hours, some 

 distinct changes could be noted as compared with the appearance of 

 shoots in sap from healthy green pears. The shoots in the latter juice, 

 while somewhat wilted, remained green and showed no discoloration. 

 The drooping and wilting of shoots in juice from blighted fruit has 

 been mentioned. In addition to this, the upper part of the stem and 

 the upper leaves were dark brown to black in color; the lower part of 

 the stem, and the midribs and the veins of the lower leaves, were of a 

 lighter brown color and became blackened after an additional twenty- 

 four hours. This appearance was very similar to that of apple shoots 



