18 A. L. PlERSTORFF 



blighted by B. amylovorus. It is possible thai oxidizing enzymes which 

 are normally present in growing tissue caused the discoloration of the 

 leaves and the stems of apple shoots inserted in the juice from blighted 

 fruit. If this is the explanation, why did not these enzymes manifest 

 themselves in twigs inserted in the juice from healthy green pears? 



To ascertain whether other fruit-rotting organisms produced toxic 

 substances similar to those noted in juice from blighted fruit, some green 

 pears were rotted by Penicillinm sp. and Scleroiinia cinerea (Bon.) 

 Wor. and the juice was expressed. No deleterious action was noted 

 when apple shoots were placed in these juices or in their cliff usates. 



Tests were made to determine whether the substance causing the 

 wilting could be precipitated by alcohol. In these tests, 100 cubic 

 centimeters of juice from blighted pears was diluted with ethyl alcohol 

 until the concentration of alcohol reached 65 per cent. At this point 

 a noticeable amount of brown organic material was precipitated. The 

 solution was filtered through filter paper, and the precipitate was allowed 

 to dry for fourteen hours so that all traces of alcohol were removed. 

 The precipitate was then redissolved in water. Apple twigs placed 

 in the solution wilted in less than two hours. 



The filtrate containing 65 per cent of alcohol was further diluted 

 so that the concentration of alcohol became 85 per cent. A very finely 

 divided light brown precipitate became visible. This was allowed to 

 stand for ten hours, the supernatant liquid was then decanted, and the 

 remainder was filtered through a high-grade filter paper. The pre- 

 cipitate, after being allowed to dry on the filter paper for fourteen 

 hours, was redissolved in 50 cubic centimeters of distilled water and the 

 cut ends of young growing apple shoots were inserted in the solution. 

 In two and one-half hours the leaves and the tips drooped, as previously 

 described. 



It was thought that perhaps the same toxic action would be exerted 

 by a culture of B. amylovorus growing in expressed green-pear juice. 

 The acidity of the sap was adjusted to pll 6.20, 6.68, and 7.80, and 

 some was left at the original concentration of pH 4.07. The cultures 

 thrived in all concentrations except pH 4.07, where growth was uncer- 

 tain. Green apple shoots placed in these solutions showed no symptoms 

 of toxic action. Similarly, cultures grown in Uschinsky's solution, con- 

 taining inulin, arbutin, amygdalin, Certo, pectin, and various sugars 

 used for enzyme tests, failed to show any harmful effects on apple 

 shoots. The concentrations of culture media were similar to those used 

 in testing for enzymes, and are given in detail under that topic. Cul- 

 tures of each of these solutions were tested with apple shoots after 

 forty-eight hours of growth, and again after five days of growth. In 

 some the organisms were killed with germicides or heat, and were tested 





